Fixed database typo and removed unnecessary class identifier.

This commit is contained in:
Batuhan Berk Başoğlu 2020-10-14 10:10:37 -04:00
parent 00ad49a143
commit 45fb349a7d
5098 changed files with 952558 additions and 85 deletions

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"""
=============================================
Integration and ODEs (:mod:`scipy.integrate`)
=============================================
.. currentmodule:: scipy.integrate
Integrating functions, given function object
============================================
.. autosummary::
:toctree: generated/
quad -- General purpose integration
quad_vec -- General purpose integration of vector-valued functions
dblquad -- General purpose double integration
tplquad -- General purpose triple integration
nquad -- General purpose N-D integration
fixed_quad -- Integrate func(x) using Gaussian quadrature of order n
quadrature -- Integrate with given tolerance using Gaussian quadrature
romberg -- Integrate func using Romberg integration
quad_explain -- Print information for use of quad
newton_cotes -- Weights and error coefficient for Newton-Cotes integration
IntegrationWarning -- Warning on issues during integration
AccuracyWarning -- Warning on issues during quadrature integration
Integrating functions, given fixed samples
==========================================
.. autosummary::
:toctree: generated/
trapz -- Use trapezoidal rule to compute integral.
cumtrapz -- Use trapezoidal rule to cumulatively compute integral.
simps -- Use Simpson's rule to compute integral from samples.
romb -- Use Romberg Integration to compute integral from
-- (2**k + 1) evenly-spaced samples.
.. seealso::
:mod:`scipy.special` for orthogonal polynomials (special) for Gaussian
quadrature roots and weights for other weighting factors and regions.
Solving initial value problems for ODE systems
==============================================
The solvers are implemented as individual classes, which can be used directly
(low-level usage) or through a convenience function.
.. autosummary::
:toctree: generated/
solve_ivp -- Convenient function for ODE integration.
RK23 -- Explicit Runge-Kutta solver of order 3(2).
RK45 -- Explicit Runge-Kutta solver of order 5(4).
DOP853 -- Explicit Runge-Kutta solver of order 8.
Radau -- Implicit Runge-Kutta solver of order 5.
BDF -- Implicit multi-step variable order (1 to 5) solver.
LSODA -- LSODA solver from ODEPACK Fortran package.
OdeSolver -- Base class for ODE solvers.
DenseOutput -- Local interpolant for computing a dense output.
OdeSolution -- Class which represents a continuous ODE solution.
Old API
-------
These are the routines developed earlier for SciPy. They wrap older solvers
implemented in Fortran (mostly ODEPACK). While the interface to them is not
particularly convenient and certain features are missing compared to the new
API, the solvers themselves are of good quality and work fast as compiled
Fortran code. In some cases, it might be worth using this old API.
.. autosummary::
:toctree: generated/
odeint -- General integration of ordinary differential equations.
ode -- Integrate ODE using VODE and ZVODE routines.
complex_ode -- Convert a complex-valued ODE to real-valued and integrate.
Solving boundary value problems for ODE systems
===============================================
.. autosummary::
:toctree: generated/
solve_bvp -- Solve a boundary value problem for a system of ODEs.
"""
from ._quadrature import *
from .odepack import *
from .quadpack import *
from ._ode import *
from ._bvp import solve_bvp
from ._ivp import (solve_ivp, OdeSolution, DenseOutput,
OdeSolver, RK23, RK45, DOP853, Radau, BDF, LSODA)
from ._quad_vec import quad_vec
__all__ = [s for s in dir() if not s.startswith('_')]
from scipy._lib._testutils import PytestTester
test = PytestTester(__name__)
del PytestTester

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"""Suite of ODE solvers implemented in Python."""
from .ivp import solve_ivp
from .rk import RK23, RK45, DOP853
from .radau import Radau
from .bdf import BDF
from .lsoda import LSODA
from .common import OdeSolution
from .base import DenseOutput, OdeSolver

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import numpy as np
def check_arguments(fun, y0, support_complex):
"""Helper function for checking arguments common to all solvers."""
y0 = np.asarray(y0)
if np.issubdtype(y0.dtype, np.complexfloating):
if not support_complex:
raise ValueError("`y0` is complex, but the chosen solver does "
"not support integration in a complex domain.")
dtype = complex
else:
dtype = float
y0 = y0.astype(dtype, copy=False)
if y0.ndim != 1:
raise ValueError("`y0` must be 1-dimensional.")
def fun_wrapped(t, y):
return np.asarray(fun(t, y), dtype=dtype)
return fun_wrapped, y0
class OdeSolver(object):
"""Base class for ODE solvers.
In order to implement a new solver you need to follow the guidelines:
1. A constructor must accept parameters presented in the base class
(listed below) along with any other parameters specific to a solver.
2. A constructor must accept arbitrary extraneous arguments
``**extraneous``, but warn that these arguments are irrelevant
using `common.warn_extraneous` function. Do not pass these
arguments to the base class.
3. A solver must implement a private method `_step_impl(self)` which
propagates a solver one step further. It must return tuple
``(success, message)``, where ``success`` is a boolean indicating
whether a step was successful, and ``message`` is a string
containing description of a failure if a step failed or None
otherwise.
4. A solver must implement a private method `_dense_output_impl(self)`,
which returns a `DenseOutput` object covering the last successful
step.
5. A solver must have attributes listed below in Attributes section.
Note that ``t_old`` and ``step_size`` are updated automatically.
6. Use `fun(self, t, y)` method for the system rhs evaluation, this
way the number of function evaluations (`nfev`) will be tracked
automatically.
7. For convenience, a base class provides `fun_single(self, t, y)` and
`fun_vectorized(self, t, y)` for evaluating the rhs in
non-vectorized and vectorized fashions respectively (regardless of
how `fun` from the constructor is implemented). These calls don't
increment `nfev`.
8. If a solver uses a Jacobian matrix and LU decompositions, it should
track the number of Jacobian evaluations (`njev`) and the number of
LU decompositions (`nlu`).
9. By convention, the function evaluations used to compute a finite
difference approximation of the Jacobian should not be counted in
`nfev`, thus use `fun_single(self, t, y)` or
`fun_vectorized(self, t, y)` when computing a finite difference
approximation of the Jacobian.
Parameters
----------
fun : callable
Right-hand side of the system. The calling signature is ``fun(t, y)``.
Here ``t`` is a scalar and there are two options for ndarray ``y``.
It can either have shape (n,), then ``fun`` must return array_like with
shape (n,). Or, alternatively, it can have shape (n, n_points), then
``fun`` must return array_like with shape (n, n_points) (each column
corresponds to a single column in ``y``). The choice between the two
options is determined by `vectorized` argument (see below).
t0 : float
Initial time.
y0 : array_like, shape (n,)
Initial state.
t_bound : float
Boundary time --- the integration won't continue beyond it. It also
determines the direction of the integration.
vectorized : bool
Whether `fun` is implemented in a vectorized fashion.
support_complex : bool, optional
Whether integration in a complex domain should be supported.
Generally determined by a derived solver class capabilities.
Default is False.
Attributes
----------
n : int
Number of equations.
status : string
Current status of the solver: 'running', 'finished' or 'failed'.
t_bound : float
Boundary time.
direction : float
Integration direction: +1 or -1.
t : float
Current time.
y : ndarray
Current state.
t_old : float
Previous time. None if no steps were made yet.
step_size : float
Size of the last successful step. None if no steps were made yet.
nfev : int
Number of the system's rhs evaluations.
njev : int
Number of the Jacobian evaluations.
nlu : int
Number of LU decompositions.
"""
TOO_SMALL_STEP = "Required step size is less than spacing between numbers."
def __init__(self, fun, t0, y0, t_bound, vectorized,
support_complex=False):
self.t_old = None
self.t = t0
self._fun, self.y = check_arguments(fun, y0, support_complex)
self.t_bound = t_bound
self.vectorized = vectorized
if vectorized:
def fun_single(t, y):
return self._fun(t, y[:, None]).ravel()
fun_vectorized = self._fun
else:
fun_single = self._fun
def fun_vectorized(t, y):
f = np.empty_like(y)
for i, yi in enumerate(y.T):
f[:, i] = self._fun(t, yi)
return f
def fun(t, y):
self.nfev += 1
return self.fun_single(t, y)
self.fun = fun
self.fun_single = fun_single
self.fun_vectorized = fun_vectorized
self.direction = np.sign(t_bound - t0) if t_bound != t0 else 1
self.n = self.y.size
self.status = 'running'
self.nfev = 0
self.njev = 0
self.nlu = 0
@property
def step_size(self):
if self.t_old is None:
return None
else:
return np.abs(self.t - self.t_old)
def step(self):
"""Perform one integration step.
Returns
-------
message : string or None
Report from the solver. Typically a reason for a failure if
`self.status` is 'failed' after the step was taken or None
otherwise.
"""
if self.status != 'running':
raise RuntimeError("Attempt to step on a failed or finished "
"solver.")
if self.n == 0 or self.t == self.t_bound:
# Handle corner cases of empty solver or no integration.
self.t_old = self.t
self.t = self.t_bound
message = None
self.status = 'finished'
else:
t = self.t
success, message = self._step_impl()
if not success:
self.status = 'failed'
else:
self.t_old = t
if self.direction * (self.t - self.t_bound) >= 0:
self.status = 'finished'
return message
def dense_output(self):
"""Compute a local interpolant over the last successful step.
Returns
-------
sol : `DenseOutput`
Local interpolant over the last successful step.
"""
if self.t_old is None:
raise RuntimeError("Dense output is available after a successful "
"step was made.")
if self.n == 0 or self.t == self.t_old:
# Handle corner cases of empty solver and no integration.
return ConstantDenseOutput(self.t_old, self.t, self.y)
else:
return self._dense_output_impl()
def _step_impl(self):
raise NotImplementedError
def _dense_output_impl(self):
raise NotImplementedError
class DenseOutput(object):
"""Base class for local interpolant over step made by an ODE solver.
It interpolates between `t_min` and `t_max` (see Attributes below).
Evaluation outside this interval is not forbidden, but the accuracy is not
guaranteed.
Attributes
----------
t_min, t_max : float
Time range of the interpolation.
"""
def __init__(self, t_old, t):
self.t_old = t_old
self.t = t
self.t_min = min(t, t_old)
self.t_max = max(t, t_old)
def __call__(self, t):
"""Evaluate the interpolant.
Parameters
----------
t : float or array_like with shape (n_points,)
Points to evaluate the solution at.
Returns
-------
y : ndarray, shape (n,) or (n, n_points)
Computed values. Shape depends on whether `t` was a scalar or a
1-D array.
"""
t = np.asarray(t)
if t.ndim > 1:
raise ValueError("`t` must be a float or a 1-D array.")
return self._call_impl(t)
def _call_impl(self, t):
raise NotImplementedError
class ConstantDenseOutput(DenseOutput):
"""Constant value interpolator.
This class used for degenerate integration cases: equal integration limits
or a system with 0 equations.
"""
def __init__(self, t_old, t, value):
super(ConstantDenseOutput, self).__init__(t_old, t)
self.value = value
def _call_impl(self, t):
if t.ndim == 0:
return self.value
else:
ret = np.empty((self.value.shape[0], t.shape[0]))
ret[:] = self.value[:, None]
return ret

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import numpy as np
from scipy.linalg import lu_factor, lu_solve
from scipy.sparse import issparse, csc_matrix, eye
from scipy.sparse.linalg import splu
from scipy.optimize._numdiff import group_columns
from .common import (validate_max_step, validate_tol, select_initial_step,
norm, EPS, num_jac, validate_first_step,
warn_extraneous)
from .base import OdeSolver, DenseOutput
MAX_ORDER = 5
NEWTON_MAXITER = 4
MIN_FACTOR = 0.2
MAX_FACTOR = 10
def compute_R(order, factor):
"""Compute the matrix for changing the differences array."""
I = np.arange(1, order + 1)[:, None]
J = np.arange(1, order + 1)
M = np.zeros((order + 1, order + 1))
M[1:, 1:] = (I - 1 - factor * J) / I
M[0] = 1
return np.cumprod(M, axis=0)
def change_D(D, order, factor):
"""Change differences array in-place when step size is changed."""
R = compute_R(order, factor)
U = compute_R(order, 1)
RU = R.dot(U)
D[:order + 1] = np.dot(RU.T, D[:order + 1])
def solve_bdf_system(fun, t_new, y_predict, c, psi, LU, solve_lu, scale, tol):
"""Solve the algebraic system resulting from BDF method."""
d = 0
y = y_predict.copy()
dy_norm_old = None
converged = False
for k in range(NEWTON_MAXITER):
f = fun(t_new, y)
if not np.all(np.isfinite(f)):
break
dy = solve_lu(LU, c * f - psi - d)
dy_norm = norm(dy / scale)
if dy_norm_old is None:
rate = None
else:
rate = dy_norm / dy_norm_old
if (rate is not None and (rate >= 1 or
rate ** (NEWTON_MAXITER - k) / (1 - rate) * dy_norm > tol)):
break
y += dy
d += dy
if (dy_norm == 0 or
rate is not None and rate / (1 - rate) * dy_norm < tol):
converged = True
break
dy_norm_old = dy_norm
return converged, k + 1, y, d
class BDF(OdeSolver):
"""Implicit method based on backward-differentiation formulas.
This is a variable order method with the order varying automatically from
1 to 5. The general framework of the BDF algorithm is described in [1]_.
This class implements a quasi-constant step size as explained in [2]_.
The error estimation strategy for the constant-step BDF is derived in [3]_.
An accuracy enhancement using modified formulas (NDF) [2]_ is also implemented.
Can be applied in the complex domain.
Parameters
----------
fun : callable
Right-hand side of the system. The calling signature is ``fun(t, y)``.
Here ``t`` is a scalar, and there are two options for the ndarray ``y``:
It can either have shape (n,); then ``fun`` must return array_like with
shape (n,). Alternatively it can have shape (n, k); then ``fun``
must return an array_like with shape (n, k), i.e. each column
corresponds to a single column in ``y``. The choice between the two
options is determined by `vectorized` argument (see below). The
vectorized implementation allows a faster approximation of the Jacobian
by finite differences (required for this solver).
t0 : float
Initial time.
y0 : array_like, shape (n,)
Initial state.
t_bound : float
Boundary time - the integration won't continue beyond it. It also
determines the direction of the integration.
first_step : float or None, optional
Initial step size. Default is ``None`` which means that the algorithm
should choose.
max_step : float, optional
Maximum allowed step size. Default is np.inf, i.e., the step size is not
bounded and determined solely by the solver.
rtol, atol : float and array_like, optional
Relative and absolute tolerances. The solver keeps the local error
estimates less than ``atol + rtol * abs(y)``. Here `rtol` controls a
relative accuracy (number of correct digits). But if a component of `y`
is approximately below `atol`, the error only needs to fall within
the same `atol` threshold, and the number of correct digits is not
guaranteed. If components of y have different scales, it might be
beneficial to set different `atol` values for different components by
passing array_like with shape (n,) for `atol`. Default values are
1e-3 for `rtol` and 1e-6 for `atol`.
jac : {None, array_like, sparse_matrix, callable}, optional
Jacobian matrix of the right-hand side of the system with respect to y,
required by this method. The Jacobian matrix has shape (n, n) and its
element (i, j) is equal to ``d f_i / d y_j``.
There are three ways to define the Jacobian:
* If array_like or sparse_matrix, the Jacobian is assumed to
be constant.
* If callable, the Jacobian is assumed to depend on both
t and y; it will be called as ``jac(t, y)`` as necessary.
For the 'Radau' and 'BDF' methods, the return value might be a
sparse matrix.
* If None (default), the Jacobian will be approximated by
finite differences.
It is generally recommended to provide the Jacobian rather than
relying on a finite-difference approximation.
jac_sparsity : {None, array_like, sparse matrix}, optional
Defines a sparsity structure of the Jacobian matrix for a
finite-difference approximation. Its shape must be (n, n). This argument
is ignored if `jac` is not `None`. If the Jacobian has only few non-zero
elements in *each* row, providing the sparsity structure will greatly
speed up the computations [4]_. A zero entry means that a corresponding
element in the Jacobian is always zero. If None (default), the Jacobian
is assumed to be dense.
vectorized : bool, optional
Whether `fun` is implemented in a vectorized fashion. Default is False.
Attributes
----------
n : int
Number of equations.
status : string
Current status of the solver: 'running', 'finished' or 'failed'.
t_bound : float
Boundary time.
direction : float
Integration direction: +1 or -1.
t : float
Current time.
y : ndarray
Current state.
t_old : float
Previous time. None if no steps were made yet.
step_size : float
Size of the last successful step. None if no steps were made yet.
nfev : int
Number of evaluations of the right-hand side.
njev : int
Number of evaluations of the Jacobian.
nlu : int
Number of LU decompositions.
References
----------
.. [1] G. D. Byrne, A. C. Hindmarsh, "A Polyalgorithm for the Numerical
Solution of Ordinary Differential Equations", ACM Transactions on
Mathematical Software, Vol. 1, No. 1, pp. 71-96, March 1975.
.. [2] L. F. Shampine, M. W. Reichelt, "THE MATLAB ODE SUITE", SIAM J. SCI.
COMPUTE., Vol. 18, No. 1, pp. 1-22, January 1997.
.. [3] E. Hairer, G. Wanner, "Solving Ordinary Differential Equations I:
Nonstiff Problems", Sec. III.2.
.. [4] A. Curtis, M. J. D. Powell, and J. Reid, "On the estimation of
sparse Jacobian matrices", Journal of the Institute of Mathematics
and its Applications, 13, pp. 117-120, 1974.
"""
def __init__(self, fun, t0, y0, t_bound, max_step=np.inf,
rtol=1e-3, atol=1e-6, jac=None, jac_sparsity=None,
vectorized=False, first_step=None, **extraneous):
warn_extraneous(extraneous)
super(BDF, self).__init__(fun, t0, y0, t_bound, vectorized,
support_complex=True)
self.max_step = validate_max_step(max_step)
self.rtol, self.atol = validate_tol(rtol, atol, self.n)
f = self.fun(self.t, self.y)
if first_step is None:
self.h_abs = select_initial_step(self.fun, self.t, self.y, f,
self.direction, 1,
self.rtol, self.atol)
else:
self.h_abs = validate_first_step(first_step, t0, t_bound)
self.h_abs_old = None
self.error_norm_old = None
self.newton_tol = max(10 * EPS / rtol, min(0.03, rtol ** 0.5))
self.jac_factor = None
self.jac, self.J = self._validate_jac(jac, jac_sparsity)
if issparse(self.J):
def lu(A):
self.nlu += 1
return splu(A)
def solve_lu(LU, b):
return LU.solve(b)
I = eye(self.n, format='csc', dtype=self.y.dtype)
else:
def lu(A):
self.nlu += 1
return lu_factor(A, overwrite_a=True)
def solve_lu(LU, b):
return lu_solve(LU, b, overwrite_b=True)
I = np.identity(self.n, dtype=self.y.dtype)
self.lu = lu
self.solve_lu = solve_lu
self.I = I
kappa = np.array([0, -0.1850, -1/9, -0.0823, -0.0415, 0])
self.gamma = np.hstack((0, np.cumsum(1 / np.arange(1, MAX_ORDER + 1))))
self.alpha = (1 - kappa) * self.gamma
self.error_const = kappa * self.gamma + 1 / np.arange(1, MAX_ORDER + 2)
D = np.empty((MAX_ORDER + 3, self.n), dtype=self.y.dtype)
D[0] = self.y
D[1] = f * self.h_abs * self.direction
self.D = D
self.order = 1
self.n_equal_steps = 0
self.LU = None
def _validate_jac(self, jac, sparsity):
t0 = self.t
y0 = self.y
if jac is None:
if sparsity is not None:
if issparse(sparsity):
sparsity = csc_matrix(sparsity)
groups = group_columns(sparsity)
sparsity = (sparsity, groups)
def jac_wrapped(t, y):
self.njev += 1
f = self.fun_single(t, y)
J, self.jac_factor = num_jac(self.fun_vectorized, t, y, f,
self.atol, self.jac_factor,
sparsity)
return J
J = jac_wrapped(t0, y0)
elif callable(jac):
J = jac(t0, y0)
self.njev += 1
if issparse(J):
J = csc_matrix(J, dtype=y0.dtype)
def jac_wrapped(t, y):
self.njev += 1
return csc_matrix(jac(t, y), dtype=y0.dtype)
else:
J = np.asarray(J, dtype=y0.dtype)
def jac_wrapped(t, y):
self.njev += 1
return np.asarray(jac(t, y), dtype=y0.dtype)
if J.shape != (self.n, self.n):
raise ValueError("`jac` is expected to have shape {}, but "
"actually has {}."
.format((self.n, self.n), J.shape))
else:
if issparse(jac):
J = csc_matrix(jac, dtype=y0.dtype)
else:
J = np.asarray(jac, dtype=y0.dtype)
if J.shape != (self.n, self.n):
raise ValueError("`jac` is expected to have shape {}, but "
"actually has {}."
.format((self.n, self.n), J.shape))
jac_wrapped = None
return jac_wrapped, J
def _step_impl(self):
t = self.t
D = self.D
max_step = self.max_step
min_step = 10 * np.abs(np.nextafter(t, self.direction * np.inf) - t)
if self.h_abs > max_step:
h_abs = max_step
change_D(D, self.order, max_step / self.h_abs)
self.n_equal_steps = 0
elif self.h_abs < min_step:
h_abs = min_step
change_D(D, self.order, min_step / self.h_abs)
self.n_equal_steps = 0
else:
h_abs = self.h_abs
atol = self.atol
rtol = self.rtol
order = self.order
alpha = self.alpha
gamma = self.gamma
error_const = self.error_const
J = self.J
LU = self.LU
current_jac = self.jac is None
step_accepted = False
while not step_accepted:
if h_abs < min_step:
return False, self.TOO_SMALL_STEP
h = h_abs * self.direction
t_new = t + h
if self.direction * (t_new - self.t_bound) > 0:
t_new = self.t_bound
change_D(D, order, np.abs(t_new - t) / h_abs)
self.n_equal_steps = 0
LU = None
h = t_new - t
h_abs = np.abs(h)
y_predict = np.sum(D[:order + 1], axis=0)
scale = atol + rtol * np.abs(y_predict)
psi = np.dot(D[1: order + 1].T, gamma[1: order + 1]) / alpha[order]
converged = False
c = h / alpha[order]
while not converged:
if LU is None:
LU = self.lu(self.I - c * J)
converged, n_iter, y_new, d = solve_bdf_system(
self.fun, t_new, y_predict, c, psi, LU, self.solve_lu,
scale, self.newton_tol)
if not converged:
if current_jac:
break
J = self.jac(t_new, y_predict)
LU = None
current_jac = True
if not converged:
factor = 0.5
h_abs *= factor
change_D(D, order, factor)
self.n_equal_steps = 0
LU = None
continue
safety = 0.9 * (2 * NEWTON_MAXITER + 1) / (2 * NEWTON_MAXITER
+ n_iter)
scale = atol + rtol * np.abs(y_new)
error = error_const[order] * d
error_norm = norm(error / scale)
if error_norm > 1:
factor = max(MIN_FACTOR,
safety * error_norm ** (-1 / (order + 1)))
h_abs *= factor
change_D(D, order, factor)
self.n_equal_steps = 0
# As we didn't have problems with convergence, we don't
# reset LU here.
else:
step_accepted = True
self.n_equal_steps += 1
self.t = t_new
self.y = y_new
self.h_abs = h_abs
self.J = J
self.LU = LU
# Update differences. The principal relation here is
# D^{j + 1} y_n = D^{j} y_n - D^{j} y_{n - 1}. Keep in mind that D
# contained difference for previous interpolating polynomial and
# d = D^{k + 1} y_n. Thus this elegant code follows.
D[order + 2] = d - D[order + 1]
D[order + 1] = d
for i in reversed(range(order + 1)):
D[i] += D[i + 1]
if self.n_equal_steps < order + 1:
return True, None
if order > 1:
error_m = error_const[order - 1] * D[order]
error_m_norm = norm(error_m / scale)
else:
error_m_norm = np.inf
if order < MAX_ORDER:
error_p = error_const[order + 1] * D[order + 2]
error_p_norm = norm(error_p / scale)
else:
error_p_norm = np.inf
error_norms = np.array([error_m_norm, error_norm, error_p_norm])
with np.errstate(divide='ignore'):
factors = error_norms ** (-1 / np.arange(order, order + 3))
delta_order = np.argmax(factors) - 1
order += delta_order
self.order = order
factor = min(MAX_FACTOR, safety * np.max(factors))
self.h_abs *= factor
change_D(D, order, factor)
self.n_equal_steps = 0
self.LU = None
return True, None
def _dense_output_impl(self):
return BdfDenseOutput(self.t_old, self.t, self.h_abs * self.direction,
self.order, self.D[:self.order + 1].copy())
class BdfDenseOutput(DenseOutput):
def __init__(self, t_old, t, h, order, D):
super(BdfDenseOutput, self).__init__(t_old, t)
self.order = order
self.t_shift = self.t - h * np.arange(self.order)
self.denom = h * (1 + np.arange(self.order))
self.D = D
def _call_impl(self, t):
if t.ndim == 0:
x = (t - self.t_shift) / self.denom
p = np.cumprod(x)
else:
x = (t - self.t_shift[:, None]) / self.denom[:, None]
p = np.cumprod(x, axis=0)
y = np.dot(self.D[1:].T, p)
if y.ndim == 1:
y += self.D[0]
else:
y += self.D[0, :, None]
return y

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@ -0,0 +1,431 @@
from itertools import groupby
from warnings import warn
import numpy as np
from scipy.sparse import find, coo_matrix
EPS = np.finfo(float).eps
def validate_first_step(first_step, t0, t_bound):
"""Assert that first_step is valid and return it."""
if first_step <= 0:
raise ValueError("`first_step` must be positive.")
if first_step > np.abs(t_bound - t0):
raise ValueError("`first_step` exceeds bounds.")
return first_step
def validate_max_step(max_step):
"""Assert that max_Step is valid and return it."""
if max_step <= 0:
raise ValueError("`max_step` must be positive.")
return max_step
def warn_extraneous(extraneous):
"""Display a warning for extraneous keyword arguments.
The initializer of each solver class is expected to collect keyword
arguments that it doesn't understand and warn about them. This function
prints a warning for each key in the supplied dictionary.
Parameters
----------
extraneous : dict
Extraneous keyword arguments
"""
if extraneous:
warn("The following arguments have no effect for a chosen solver: {}."
.format(", ".join("`{}`".format(x) for x in extraneous)))
def validate_tol(rtol, atol, n):
"""Validate tolerance values."""
if rtol < 100 * EPS:
warn("`rtol` is too low, setting to {}".format(100 * EPS))
rtol = 100 * EPS
atol = np.asarray(atol)
if atol.ndim > 0 and atol.shape != (n,):
raise ValueError("`atol` has wrong shape.")
if np.any(atol < 0):
raise ValueError("`atol` must be positive.")
return rtol, atol
def norm(x):
"""Compute RMS norm."""
return np.linalg.norm(x) / x.size ** 0.5
def select_initial_step(fun, t0, y0, f0, direction, order, rtol, atol):
"""Empirically select a good initial step.
The algorithm is described in [1]_.
Parameters
----------
fun : callable
Right-hand side of the system.
t0 : float
Initial value of the independent variable.
y0 : ndarray, shape (n,)
Initial value of the dependent variable.
f0 : ndarray, shape (n,)
Initial value of the derivative, i.e., ``fun(t0, y0)``.
direction : float
Integration direction.
order : float
Error estimator order. It means that the error controlled by the
algorithm is proportional to ``step_size ** (order + 1)`.
rtol : float
Desired relative tolerance.
atol : float
Desired absolute tolerance.
Returns
-------
h_abs : float
Absolute value of the suggested initial step.
References
----------
.. [1] E. Hairer, S. P. Norsett G. Wanner, "Solving Ordinary Differential
Equations I: Nonstiff Problems", Sec. II.4.
"""
if y0.size == 0:
return np.inf
scale = atol + np.abs(y0) * rtol
d0 = norm(y0 / scale)
d1 = norm(f0 / scale)
if d0 < 1e-5 or d1 < 1e-5:
h0 = 1e-6
else:
h0 = 0.01 * d0 / d1
y1 = y0 + h0 * direction * f0
f1 = fun(t0 + h0 * direction, y1)
d2 = norm((f1 - f0) / scale) / h0
if d1 <= 1e-15 and d2 <= 1e-15:
h1 = max(1e-6, h0 * 1e-3)
else:
h1 = (0.01 / max(d1, d2)) ** (1 / (order + 1))
return min(100 * h0, h1)
class OdeSolution(object):
"""Continuous ODE solution.
It is organized as a collection of `DenseOutput` objects which represent
local interpolants. It provides an algorithm to select a right interpolant
for each given point.
The interpolants cover the range between `t_min` and `t_max` (see
Attributes below). Evaluation outside this interval is not forbidden, but
the accuracy is not guaranteed.
When evaluating at a breakpoint (one of the values in `ts`) a segment with
the lower index is selected.
Parameters
----------
ts : array_like, shape (n_segments + 1,)
Time instants between which local interpolants are defined. Must
be strictly increasing or decreasing (zero segment with two points is
also allowed).
interpolants : list of DenseOutput with n_segments elements
Local interpolants. An i-th interpolant is assumed to be defined
between ``ts[i]`` and ``ts[i + 1]``.
Attributes
----------
t_min, t_max : float
Time range of the interpolation.
"""
def __init__(self, ts, interpolants):
ts = np.asarray(ts)
d = np.diff(ts)
# The first case covers integration on zero segment.
if not ((ts.size == 2 and ts[0] == ts[-1])
or np.all(d > 0) or np.all(d < 0)):
raise ValueError("`ts` must be strictly increasing or decreasing.")
self.n_segments = len(interpolants)
if ts.shape != (self.n_segments + 1,):
raise ValueError("Numbers of time stamps and interpolants "
"don't match.")
self.ts = ts
self.interpolants = interpolants
if ts[-1] >= ts[0]:
self.t_min = ts[0]
self.t_max = ts[-1]
self.ascending = True
self.ts_sorted = ts
else:
self.t_min = ts[-1]
self.t_max = ts[0]
self.ascending = False
self.ts_sorted = ts[::-1]
def _call_single(self, t):
# Here we preserve a certain symmetry that when t is in self.ts,
# then we prioritize a segment with a lower index.
if self.ascending:
ind = np.searchsorted(self.ts_sorted, t, side='left')
else:
ind = np.searchsorted(self.ts_sorted, t, side='right')
segment = min(max(ind - 1, 0), self.n_segments - 1)
if not self.ascending:
segment = self.n_segments - 1 - segment
return self.interpolants[segment](t)
def __call__(self, t):
"""Evaluate the solution.
Parameters
----------
t : float or array_like with shape (n_points,)
Points to evaluate at.
Returns
-------
y : ndarray, shape (n_states,) or (n_states, n_points)
Computed values. Shape depends on whether `t` is a scalar or a
1-D array.
"""
t = np.asarray(t)
if t.ndim == 0:
return self._call_single(t)
order = np.argsort(t)
reverse = np.empty_like(order)
reverse[order] = np.arange(order.shape[0])
t_sorted = t[order]
# See comment in self._call_single.
if self.ascending:
segments = np.searchsorted(self.ts_sorted, t_sorted, side='left')
else:
segments = np.searchsorted(self.ts_sorted, t_sorted, side='right')
segments -= 1
segments[segments < 0] = 0
segments[segments > self.n_segments - 1] = self.n_segments - 1
if not self.ascending:
segments = self.n_segments - 1 - segments
ys = []
group_start = 0
for segment, group in groupby(segments):
group_end = group_start + len(list(group))
y = self.interpolants[segment](t_sorted[group_start:group_end])
ys.append(y)
group_start = group_end
ys = np.hstack(ys)
ys = ys[:, reverse]
return ys
NUM_JAC_DIFF_REJECT = EPS ** 0.875
NUM_JAC_DIFF_SMALL = EPS ** 0.75
NUM_JAC_DIFF_BIG = EPS ** 0.25
NUM_JAC_MIN_FACTOR = 1e3 * EPS
NUM_JAC_FACTOR_INCREASE = 10
NUM_JAC_FACTOR_DECREASE = 0.1
def num_jac(fun, t, y, f, threshold, factor, sparsity=None):
"""Finite differences Jacobian approximation tailored for ODE solvers.
This function computes finite difference approximation to the Jacobian
matrix of `fun` with respect to `y` using forward differences.
The Jacobian matrix has shape (n, n) and its element (i, j) is equal to
``d f_i / d y_j``.
A special feature of this function is the ability to correct the step
size from iteration to iteration. The main idea is to keep the finite
difference significantly separated from its round-off error which
approximately equals ``EPS * np.abs(f)``. It reduces a possibility of a
huge error and assures that the estimated derivative are reasonably close
to the true values (i.e., the finite difference approximation is at least
qualitatively reflects the structure of the true Jacobian).
Parameters
----------
fun : callable
Right-hand side of the system implemented in a vectorized fashion.
t : float
Current time.
y : ndarray, shape (n,)
Current state.
f : ndarray, shape (n,)
Value of the right hand side at (t, y).
threshold : float
Threshold for `y` value used for computing the step size as
``factor * np.maximum(np.abs(y), threshold)``. Typically, the value of
absolute tolerance (atol) for a solver should be passed as `threshold`.
factor : ndarray with shape (n,) or None
Factor to use for computing the step size. Pass None for the very
evaluation, then use the value returned from this function.
sparsity : tuple (structure, groups) or None
Sparsity structure of the Jacobian, `structure` must be csc_matrix.
Returns
-------
J : ndarray or csc_matrix, shape (n, n)
Jacobian matrix.
factor : ndarray, shape (n,)
Suggested `factor` for the next evaluation.
"""
y = np.asarray(y)
n = y.shape[0]
if n == 0:
return np.empty((0, 0)), factor
if factor is None:
factor = np.full(n, EPS ** 0.5)
else:
factor = factor.copy()
# Direct the step as ODE dictates, hoping that such a step won't lead to
# a problematic region. For complex ODEs it makes sense to use the real
# part of f as we use steps along real axis.
f_sign = 2 * (np.real(f) >= 0).astype(float) - 1
y_scale = f_sign * np.maximum(threshold, np.abs(y))
h = (y + factor * y_scale) - y
# Make sure that the step is not 0 to start with. Not likely it will be
# executed often.
for i in np.nonzero(h == 0)[0]:
while h[i] == 0:
factor[i] *= 10
h[i] = (y[i] + factor[i] * y_scale[i]) - y[i]
if sparsity is None:
return _dense_num_jac(fun, t, y, f, h, factor, y_scale)
else:
structure, groups = sparsity
return _sparse_num_jac(fun, t, y, f, h, factor, y_scale,
structure, groups)
def _dense_num_jac(fun, t, y, f, h, factor, y_scale):
n = y.shape[0]
h_vecs = np.diag(h)
f_new = fun(t, y[:, None] + h_vecs)
diff = f_new - f[:, None]
max_ind = np.argmax(np.abs(diff), axis=0)
r = np.arange(n)
max_diff = np.abs(diff[max_ind, r])
scale = np.maximum(np.abs(f[max_ind]), np.abs(f_new[max_ind, r]))
diff_too_small = max_diff < NUM_JAC_DIFF_REJECT * scale
if np.any(diff_too_small):
ind, = np.nonzero(diff_too_small)
new_factor = NUM_JAC_FACTOR_INCREASE * factor[ind]
h_new = (y[ind] + new_factor * y_scale[ind]) - y[ind]
h_vecs[ind, ind] = h_new
f_new = fun(t, y[:, None] + h_vecs[:, ind])
diff_new = f_new - f[:, None]
max_ind = np.argmax(np.abs(diff_new), axis=0)
r = np.arange(ind.shape[0])
max_diff_new = np.abs(diff_new[max_ind, r])
scale_new = np.maximum(np.abs(f[max_ind]), np.abs(f_new[max_ind, r]))
update = max_diff[ind] * scale_new < max_diff_new * scale[ind]
if np.any(update):
update, = np.nonzero(update)
update_ind = ind[update]
factor[update_ind] = new_factor[update]
h[update_ind] = h_new[update]
diff[:, update_ind] = diff_new[:, update]
scale[update_ind] = scale_new[update]
max_diff[update_ind] = max_diff_new[update]
diff /= h
factor[max_diff < NUM_JAC_DIFF_SMALL * scale] *= NUM_JAC_FACTOR_INCREASE
factor[max_diff > NUM_JAC_DIFF_BIG * scale] *= NUM_JAC_FACTOR_DECREASE
factor = np.maximum(factor, NUM_JAC_MIN_FACTOR)
return diff, factor
def _sparse_num_jac(fun, t, y, f, h, factor, y_scale, structure, groups):
n = y.shape[0]
n_groups = np.max(groups) + 1
h_vecs = np.empty((n_groups, n))
for group in range(n_groups):
e = np.equal(group, groups)
h_vecs[group] = h * e
h_vecs = h_vecs.T
f_new = fun(t, y[:, None] + h_vecs)
df = f_new - f[:, None]
i, j, _ = find(structure)
diff = coo_matrix((df[i, groups[j]], (i, j)), shape=(n, n)).tocsc()
max_ind = np.array(abs(diff).argmax(axis=0)).ravel()
r = np.arange(n)
max_diff = np.asarray(np.abs(diff[max_ind, r])).ravel()
scale = np.maximum(np.abs(f[max_ind]),
np.abs(f_new[max_ind, groups[r]]))
diff_too_small = max_diff < NUM_JAC_DIFF_REJECT * scale
if np.any(diff_too_small):
ind, = np.nonzero(diff_too_small)
new_factor = NUM_JAC_FACTOR_INCREASE * factor[ind]
h_new = (y[ind] + new_factor * y_scale[ind]) - y[ind]
h_new_all = np.zeros(n)
h_new_all[ind] = h_new
groups_unique = np.unique(groups[ind])
groups_map = np.empty(n_groups, dtype=int)
h_vecs = np.empty((groups_unique.shape[0], n))
for k, group in enumerate(groups_unique):
e = np.equal(group, groups)
h_vecs[k] = h_new_all * e
groups_map[group] = k
h_vecs = h_vecs.T
f_new = fun(t, y[:, None] + h_vecs)
df = f_new - f[:, None]
i, j, _ = find(structure[:, ind])
diff_new = coo_matrix((df[i, groups_map[groups[ind[j]]]],
(i, j)), shape=(n, ind.shape[0])).tocsc()
max_ind_new = np.array(abs(diff_new).argmax(axis=0)).ravel()
r = np.arange(ind.shape[0])
max_diff_new = np.asarray(np.abs(diff_new[max_ind_new, r])).ravel()
scale_new = np.maximum(
np.abs(f[max_ind_new]),
np.abs(f_new[max_ind_new, groups_map[groups[ind]]]))
update = max_diff[ind] * scale_new < max_diff_new * scale[ind]
if np.any(update):
update, = np.nonzero(update)
update_ind = ind[update]
factor[update_ind] = new_factor[update]
h[update_ind] = h_new[update]
diff[:, update_ind] = diff_new[:, update]
scale[update_ind] = scale_new[update]
max_diff[update_ind] = max_diff_new[update]
diff.data /= np.repeat(h, np.diff(diff.indptr))
factor[max_diff < NUM_JAC_DIFF_SMALL * scale] *= NUM_JAC_FACTOR_INCREASE
factor[max_diff > NUM_JAC_DIFF_BIG * scale] *= NUM_JAC_FACTOR_DECREASE
factor = np.maximum(factor, NUM_JAC_MIN_FACTOR)
return diff, factor

View file

@ -0,0 +1,193 @@
import numpy as np
N_STAGES = 12
N_STAGES_EXTENDED = 16
INTERPOLATOR_POWER = 7
C = np.array([0.0,
0.526001519587677318785587544488e-01,
0.789002279381515978178381316732e-01,
0.118350341907227396726757197510,
0.281649658092772603273242802490,
0.333333333333333333333333333333,
0.25,
0.307692307692307692307692307692,
0.651282051282051282051282051282,
0.6,
0.857142857142857142857142857142,
1.0,
1.0,
0.1,
0.2,
0.777777777777777777777777777778])
A = np.zeros((N_STAGES_EXTENDED, N_STAGES_EXTENDED))
A[1, 0] = 5.26001519587677318785587544488e-2
A[2, 0] = 1.97250569845378994544595329183e-2
A[2, 1] = 5.91751709536136983633785987549e-2
A[3, 0] = 2.95875854768068491816892993775e-2
A[3, 2] = 8.87627564304205475450678981324e-2
A[4, 0] = 2.41365134159266685502369798665e-1
A[4, 2] = -8.84549479328286085344864962717e-1
A[4, 3] = 9.24834003261792003115737966543e-1
A[5, 0] = 3.7037037037037037037037037037e-2
A[5, 3] = 1.70828608729473871279604482173e-1
A[5, 4] = 1.25467687566822425016691814123e-1
A[6, 0] = 3.7109375e-2
A[6, 3] = 1.70252211019544039314978060272e-1
A[6, 4] = 6.02165389804559606850219397283e-2
A[6, 5] = -1.7578125e-2
A[7, 0] = 3.70920001185047927108779319836e-2
A[7, 3] = 1.70383925712239993810214054705e-1
A[7, 4] = 1.07262030446373284651809199168e-1
A[7, 5] = -1.53194377486244017527936158236e-2
A[7, 6] = 8.27378916381402288758473766002e-3
A[8, 0] = 6.24110958716075717114429577812e-1
A[8, 3] = -3.36089262944694129406857109825
A[8, 4] = -8.68219346841726006818189891453e-1
A[8, 5] = 2.75920996994467083049415600797e1
A[8, 6] = 2.01540675504778934086186788979e1
A[8, 7] = -4.34898841810699588477366255144e1
A[9, 0] = 4.77662536438264365890433908527e-1
A[9, 3] = -2.48811461997166764192642586468
A[9, 4] = -5.90290826836842996371446475743e-1
A[9, 5] = 2.12300514481811942347288949897e1
A[9, 6] = 1.52792336328824235832596922938e1
A[9, 7] = -3.32882109689848629194453265587e1
A[9, 8] = -2.03312017085086261358222928593e-2
A[10, 0] = -9.3714243008598732571704021658e-1
A[10, 3] = 5.18637242884406370830023853209
A[10, 4] = 1.09143734899672957818500254654
A[10, 5] = -8.14978701074692612513997267357
A[10, 6] = -1.85200656599969598641566180701e1
A[10, 7] = 2.27394870993505042818970056734e1
A[10, 8] = 2.49360555267965238987089396762
A[10, 9] = -3.0467644718982195003823669022
A[11, 0] = 2.27331014751653820792359768449
A[11, 3] = -1.05344954667372501984066689879e1
A[11, 4] = -2.00087205822486249909675718444
A[11, 5] = -1.79589318631187989172765950534e1
A[11, 6] = 2.79488845294199600508499808837e1
A[11, 7] = -2.85899827713502369474065508674
A[11, 8] = -8.87285693353062954433549289258
A[11, 9] = 1.23605671757943030647266201528e1
A[11, 10] = 6.43392746015763530355970484046e-1
A[12, 0] = 5.42937341165687622380535766363e-2
A[12, 5] = 4.45031289275240888144113950566
A[12, 6] = 1.89151789931450038304281599044
A[12, 7] = -5.8012039600105847814672114227
A[12, 8] = 3.1116436695781989440891606237e-1
A[12, 9] = -1.52160949662516078556178806805e-1
A[12, 10] = 2.01365400804030348374776537501e-1
A[12, 11] = 4.47106157277725905176885569043e-2
A[13, 0] = 5.61675022830479523392909219681e-2
A[13, 6] = 2.53500210216624811088794765333e-1
A[13, 7] = -2.46239037470802489917441475441e-1
A[13, 8] = -1.24191423263816360469010140626e-1
A[13, 9] = 1.5329179827876569731206322685e-1
A[13, 10] = 8.20105229563468988491666602057e-3
A[13, 11] = 7.56789766054569976138603589584e-3
A[13, 12] = -8.298e-3
A[14, 0] = 3.18346481635021405060768473261e-2
A[14, 5] = 2.83009096723667755288322961402e-2
A[14, 6] = 5.35419883074385676223797384372e-2
A[14, 7] = -5.49237485713909884646569340306e-2
A[14, 10] = -1.08347328697249322858509316994e-4
A[14, 11] = 3.82571090835658412954920192323e-4
A[14, 12] = -3.40465008687404560802977114492e-4
A[14, 13] = 1.41312443674632500278074618366e-1
A[15, 0] = -4.28896301583791923408573538692e-1
A[15, 5] = -4.69762141536116384314449447206
A[15, 6] = 7.68342119606259904184240953878
A[15, 7] = 4.06898981839711007970213554331
A[15, 8] = 3.56727187455281109270669543021e-1
A[15, 12] = -1.39902416515901462129418009734e-3
A[15, 13] = 2.9475147891527723389556272149
A[15, 14] = -9.15095847217987001081870187138
B = A[N_STAGES, :N_STAGES]
E3 = np.zeros(N_STAGES + 1)
E3[:-1] = B.copy()
E3[0] -= 0.244094488188976377952755905512
E3[8] -= 0.733846688281611857341361741547
E3[11] -= 0.220588235294117647058823529412e-1
E5 = np.zeros(N_STAGES + 1)
E5[0] = 0.1312004499419488073250102996e-1
E5[5] = -0.1225156446376204440720569753e+1
E5[6] = -0.4957589496572501915214079952
E5[7] = 0.1664377182454986536961530415e+1
E5[8] = -0.3503288487499736816886487290
E5[9] = 0.3341791187130174790297318841
E5[10] = 0.8192320648511571246570742613e-1
E5[11] = -0.2235530786388629525884427845e-1
# First 3 coefficients are computed separately.
D = np.zeros((INTERPOLATOR_POWER - 3, N_STAGES_EXTENDED))
D[0, 0] = -0.84289382761090128651353491142e+1
D[0, 5] = 0.56671495351937776962531783590
D[0, 6] = -0.30689499459498916912797304727e+1
D[0, 7] = 0.23846676565120698287728149680e+1
D[0, 8] = 0.21170345824450282767155149946e+1
D[0, 9] = -0.87139158377797299206789907490
D[0, 10] = 0.22404374302607882758541771650e+1
D[0, 11] = 0.63157877876946881815570249290
D[0, 12] = -0.88990336451333310820698117400e-1
D[0, 13] = 0.18148505520854727256656404962e+2
D[0, 14] = -0.91946323924783554000451984436e+1
D[0, 15] = -0.44360363875948939664310572000e+1
D[1, 0] = 0.10427508642579134603413151009e+2
D[1, 5] = 0.24228349177525818288430175319e+3
D[1, 6] = 0.16520045171727028198505394887e+3
D[1, 7] = -0.37454675472269020279518312152e+3
D[1, 8] = -0.22113666853125306036270938578e+2
D[1, 9] = 0.77334326684722638389603898808e+1
D[1, 10] = -0.30674084731089398182061213626e+2
D[1, 11] = -0.93321305264302278729567221706e+1
D[1, 12] = 0.15697238121770843886131091075e+2
D[1, 13] = -0.31139403219565177677282850411e+2
D[1, 14] = -0.93529243588444783865713862664e+1
D[1, 15] = 0.35816841486394083752465898540e+2
D[2, 0] = 0.19985053242002433820987653617e+2
D[2, 5] = -0.38703730874935176555105901742e+3
D[2, 6] = -0.18917813819516756882830838328e+3
D[2, 7] = 0.52780815920542364900561016686e+3
D[2, 8] = -0.11573902539959630126141871134e+2
D[2, 9] = 0.68812326946963000169666922661e+1
D[2, 10] = -0.10006050966910838403183860980e+1
D[2, 11] = 0.77771377980534432092869265740
D[2, 12] = -0.27782057523535084065932004339e+1
D[2, 13] = -0.60196695231264120758267380846e+2
D[2, 14] = 0.84320405506677161018159903784e+2
D[2, 15] = 0.11992291136182789328035130030e+2
D[3, 0] = -0.25693933462703749003312586129e+2
D[3, 5] = -0.15418974869023643374053993627e+3
D[3, 6] = -0.23152937917604549567536039109e+3
D[3, 7] = 0.35763911791061412378285349910e+3
D[3, 8] = 0.93405324183624310003907691704e+2
D[3, 9] = -0.37458323136451633156875139351e+2
D[3, 10] = 0.10409964950896230045147246184e+3
D[3, 11] = 0.29840293426660503123344363579e+2
D[3, 12] = -0.43533456590011143754432175058e+2
D[3, 13] = 0.96324553959188282948394950600e+2
D[3, 14] = -0.39177261675615439165231486172e+2
D[3, 15] = -0.14972683625798562581422125276e+3

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@ -0,0 +1,663 @@
import inspect
import numpy as np
from .bdf import BDF
from .radau import Radau
from .rk import RK23, RK45, DOP853
from .lsoda import LSODA
from scipy.optimize import OptimizeResult
from .common import EPS, OdeSolution
from .base import OdeSolver
METHODS = {'RK23': RK23,
'RK45': RK45,
'DOP853': DOP853,
'Radau': Radau,
'BDF': BDF,
'LSODA': LSODA}
MESSAGES = {0: "The solver successfully reached the end of the integration interval.",
1: "A termination event occurred."}
class OdeResult(OptimizeResult):
pass
def prepare_events(events):
"""Standardize event functions and extract is_terminal and direction."""
if callable(events):
events = (events,)
if events is not None:
is_terminal = np.empty(len(events), dtype=bool)
direction = np.empty(len(events))
for i, event in enumerate(events):
try:
is_terminal[i] = event.terminal
except AttributeError:
is_terminal[i] = False
try:
direction[i] = event.direction
except AttributeError:
direction[i] = 0
else:
is_terminal = None
direction = None
return events, is_terminal, direction
def solve_event_equation(event, sol, t_old, t):
"""Solve an equation corresponding to an ODE event.
The equation is ``event(t, y(t)) = 0``, here ``y(t)`` is known from an
ODE solver using some sort of interpolation. It is solved by
`scipy.optimize.brentq` with xtol=atol=4*EPS.
Parameters
----------
event : callable
Function ``event(t, y)``.
sol : callable
Function ``sol(t)`` which evaluates an ODE solution between `t_old`
and `t`.
t_old, t : float
Previous and new values of time. They will be used as a bracketing
interval.
Returns
-------
root : float
Found solution.
"""
from scipy.optimize import brentq
return brentq(lambda t: event(t, sol(t)), t_old, t,
xtol=4 * EPS, rtol=4 * EPS)
def handle_events(sol, events, active_events, is_terminal, t_old, t):
"""Helper function to handle events.
Parameters
----------
sol : DenseOutput
Function ``sol(t)`` which evaluates an ODE solution between `t_old`
and `t`.
events : list of callables, length n_events
Event functions with signatures ``event(t, y)``.
active_events : ndarray
Indices of events which occurred.
is_terminal : ndarray, shape (n_events,)
Which events are terminal.
t_old, t : float
Previous and new values of time.
Returns
-------
root_indices : ndarray
Indices of events which take zero between `t_old` and `t` and before
a possible termination.
roots : ndarray
Values of t at which events occurred.
terminate : bool
Whether a terminal event occurred.
"""
roots = [solve_event_equation(events[event_index], sol, t_old, t)
for event_index in active_events]
roots = np.asarray(roots)
if np.any(is_terminal[active_events]):
if t > t_old:
order = np.argsort(roots)
else:
order = np.argsort(-roots)
active_events = active_events[order]
roots = roots[order]
t = np.nonzero(is_terminal[active_events])[0][0]
active_events = active_events[:t + 1]
roots = roots[:t + 1]
terminate = True
else:
terminate = False
return active_events, roots, terminate
def find_active_events(g, g_new, direction):
"""Find which event occurred during an integration step.
Parameters
----------
g, g_new : array_like, shape (n_events,)
Values of event functions at a current and next points.
direction : ndarray, shape (n_events,)
Event "direction" according to the definition in `solve_ivp`.
Returns
-------
active_events : ndarray
Indices of events which occurred during the step.
"""
g, g_new = np.asarray(g), np.asarray(g_new)
up = (g <= 0) & (g_new >= 0)
down = (g >= 0) & (g_new <= 0)
either = up | down
mask = (up & (direction > 0) |
down & (direction < 0) |
either & (direction == 0))
return np.nonzero(mask)[0]
def solve_ivp(fun, t_span, y0, method='RK45', t_eval=None, dense_output=False,
events=None, vectorized=False, args=None, **options):
"""Solve an initial value problem for a system of ODEs.
This function numerically integrates a system of ordinary differential
equations given an initial value::
dy / dt = f(t, y)
y(t0) = y0
Here t is a 1-D independent variable (time), y(t) is an
N-D vector-valued function (state), and an N-D
vector-valued function f(t, y) determines the differential equations.
The goal is to find y(t) approximately satisfying the differential
equations, given an initial value y(t0)=y0.
Some of the solvers support integration in the complex domain, but note
that for stiff ODE solvers, the right-hand side must be
complex-differentiable (satisfy Cauchy-Riemann equations [11]_).
To solve a problem in the complex domain, pass y0 with a complex data type.
Another option always available is to rewrite your problem for real and
imaginary parts separately.
Parameters
----------
fun : callable
Right-hand side of the system. The calling signature is ``fun(t, y)``.
Here `t` is a scalar, and there are two options for the ndarray `y`:
It can either have shape (n,); then `fun` must return array_like with
shape (n,). Alternatively, it can have shape (n, k); then `fun`
must return an array_like with shape (n, k), i.e., each column
corresponds to a single column in `y`. The choice between the two
options is determined by `vectorized` argument (see below). The
vectorized implementation allows a faster approximation of the Jacobian
by finite differences (required for stiff solvers).
t_span : 2-tuple of floats
Interval of integration (t0, tf). The solver starts with t=t0 and
integrates until it reaches t=tf.
y0 : array_like, shape (n,)
Initial state. For problems in the complex domain, pass `y0` with a
complex data type (even if the initial value is purely real).
method : string or `OdeSolver`, optional
Integration method to use:
* 'RK45' (default): Explicit Runge-Kutta method of order 5(4) [1]_.
The error is controlled assuming accuracy of the fourth-order
method, but steps are taken using the fifth-order accurate
formula (local extrapolation is done). A quartic interpolation
polynomial is used for the dense output [2]_. Can be applied in
the complex domain.
* 'RK23': Explicit Runge-Kutta method of order 3(2) [3]_. The error
is controlled assuming accuracy of the second-order method, but
steps are taken using the third-order accurate formula (local
extrapolation is done). A cubic Hermite polynomial is used for the
dense output. Can be applied in the complex domain.
* 'DOP853': Explicit Runge-Kutta method of order 8 [13]_.
Python implementation of the "DOP853" algorithm originally
written in Fortran [14]_. A 7-th order interpolation polynomial
accurate to 7-th order is used for the dense output.
Can be applied in the complex domain.
* 'Radau': Implicit Runge-Kutta method of the Radau IIA family of
order 5 [4]_. The error is controlled with a third-order accurate
embedded formula. A cubic polynomial which satisfies the
collocation conditions is used for the dense output.
* 'BDF': Implicit multi-step variable-order (1 to 5) method based
on a backward differentiation formula for the derivative
approximation [5]_. The implementation follows the one described
in [6]_. A quasi-constant step scheme is used and accuracy is
enhanced using the NDF modification. Can be applied in the
complex domain.
* 'LSODA': Adams/BDF method with automatic stiffness detection and
switching [7]_, [8]_. This is a wrapper of the Fortran solver
from ODEPACK.
Explicit Runge-Kutta methods ('RK23', 'RK45', 'DOP853') should be used
for non-stiff problems and implicit methods ('Radau', 'BDF') for
stiff problems [9]_. Among Runge-Kutta methods, 'DOP853' is recommended
for solving with high precision (low values of `rtol` and `atol`).
If not sure, first try to run 'RK45'. If it makes unusually many
iterations, diverges, or fails, your problem is likely to be stiff and
you should use 'Radau' or 'BDF'. 'LSODA' can also be a good universal
choice, but it might be somewhat less convenient to work with as it
wraps old Fortran code.
You can also pass an arbitrary class derived from `OdeSolver` which
implements the solver.
t_eval : array_like or None, optional
Times at which to store the computed solution, must be sorted and lie
within `t_span`. If None (default), use points selected by the solver.
dense_output : bool, optional
Whether to compute a continuous solution. Default is False.
events : callable, or list of callables, optional
Events to track. If None (default), no events will be tracked.
Each event occurs at the zeros of a continuous function of time and
state. Each function must have the signature ``event(t, y)`` and return
a float. The solver will find an accurate value of `t` at which
``event(t, y(t)) = 0`` using a root-finding algorithm. By default, all
zeros will be found. The solver looks for a sign change over each step,
so if multiple zero crossings occur within one step, events may be
missed. Additionally each `event` function might have the following
attributes:
terminal: bool, optional
Whether to terminate integration if this event occurs.
Implicitly False if not assigned.
direction: float, optional
Direction of a zero crossing. If `direction` is positive,
`event` will only trigger when going from negative to positive,
and vice versa if `direction` is negative. If 0, then either
direction will trigger event. Implicitly 0 if not assigned.
You can assign attributes like ``event.terminal = True`` to any
function in Python.
vectorized : bool, optional
Whether `fun` is implemented in a vectorized fashion. Default is False.
args : tuple, optional
Additional arguments to pass to the user-defined functions. If given,
the additional arguments are passed to all user-defined functions.
So if, for example, `fun` has the signature ``fun(t, y, a, b, c)``,
then `jac` (if given) and any event functions must have the same
signature, and `args` must be a tuple of length 3.
options
Options passed to a chosen solver. All options available for already
implemented solvers are listed below.
first_step : float or None, optional
Initial step size. Default is `None` which means that the algorithm
should choose.
max_step : float, optional
Maximum allowed step size. Default is np.inf, i.e., the step size is not
bounded and determined solely by the solver.
rtol, atol : float or array_like, optional
Relative and absolute tolerances. The solver keeps the local error
estimates less than ``atol + rtol * abs(y)``. Here `rtol` controls a
relative accuracy (number of correct digits). But if a component of `y`
is approximately below `atol`, the error only needs to fall within
the same `atol` threshold, and the number of correct digits is not
guaranteed. If components of y have different scales, it might be
beneficial to set different `atol` values for different components by
passing array_like with shape (n,) for `atol`. Default values are
1e-3 for `rtol` and 1e-6 for `atol`.
jac : array_like, sparse_matrix, callable or None, optional
Jacobian matrix of the right-hand side of the system with respect
to y, required by the 'Radau', 'BDF' and 'LSODA' method. The
Jacobian matrix has shape (n, n) and its element (i, j) is equal to
``d f_i / d y_j``. There are three ways to define the Jacobian:
* If array_like or sparse_matrix, the Jacobian is assumed to
be constant. Not supported by 'LSODA'.
* If callable, the Jacobian is assumed to depend on both
t and y; it will be called as ``jac(t, y)``, as necessary.
For 'Radau' and 'BDF' methods, the return value might be a
sparse matrix.
* If None (default), the Jacobian will be approximated by
finite differences.
It is generally recommended to provide the Jacobian rather than
relying on a finite-difference approximation.
jac_sparsity : array_like, sparse matrix or None, optional
Defines a sparsity structure of the Jacobian matrix for a finite-
difference approximation. Its shape must be (n, n). This argument
is ignored if `jac` is not `None`. If the Jacobian has only few
non-zero elements in *each* row, providing the sparsity structure
will greatly speed up the computations [10]_. A zero entry means that
a corresponding element in the Jacobian is always zero. If None
(default), the Jacobian is assumed to be dense.
Not supported by 'LSODA', see `lband` and `uband` instead.
lband, uband : int or None, optional
Parameters defining the bandwidth of the Jacobian for the 'LSODA'
method, i.e., ``jac[i, j] != 0 only for i - lband <= j <= i + uband``.
Default is None. Setting these requires your jac routine to return the
Jacobian in the packed format: the returned array must have ``n``
columns and ``uband + lband + 1`` rows in which Jacobian diagonals are
written. Specifically ``jac_packed[uband + i - j , j] = jac[i, j]``.
The same format is used in `scipy.linalg.solve_banded` (check for an
illustration). These parameters can be also used with ``jac=None`` to
reduce the number of Jacobian elements estimated by finite differences.
min_step : float, optional
The minimum allowed step size for 'LSODA' method.
By default `min_step` is zero.
Returns
-------
Bunch object with the following fields defined:
t : ndarray, shape (n_points,)
Time points.
y : ndarray, shape (n, n_points)
Values of the solution at `t`.
sol : `OdeSolution` or None
Found solution as `OdeSolution` instance; None if `dense_output` was
set to False.
t_events : list of ndarray or None
Contains for each event type a list of arrays at which an event of
that type event was detected. None if `events` was None.
y_events : list of ndarray or None
For each value of `t_events`, the corresponding value of the solution.
None if `events` was None.
nfev : int
Number of evaluations of the right-hand side.
njev : int
Number of evaluations of the Jacobian.
nlu : int
Number of LU decompositions.
status : int
Reason for algorithm termination:
* -1: Integration step failed.
* 0: The solver successfully reached the end of `tspan`.
* 1: A termination event occurred.
message : string
Human-readable description of the termination reason.
success : bool
True if the solver reached the interval end or a termination event
occurred (``status >= 0``).
References
----------
.. [1] J. R. Dormand, P. J. Prince, "A family of embedded Runge-Kutta
formulae", Journal of Computational and Applied Mathematics, Vol. 6,
No. 1, pp. 19-26, 1980.
.. [2] L. W. Shampine, "Some Practical Runge-Kutta Formulas", Mathematics
of Computation,, Vol. 46, No. 173, pp. 135-150, 1986.
.. [3] P. Bogacki, L.F. Shampine, "A 3(2) Pair of Runge-Kutta Formulas",
Appl. Math. Lett. Vol. 2, No. 4. pp. 321-325, 1989.
.. [4] E. Hairer, G. Wanner, "Solving Ordinary Differential Equations II:
Stiff and Differential-Algebraic Problems", Sec. IV.8.
.. [5] `Backward Differentiation Formula
<https://en.wikipedia.org/wiki/Backward_differentiation_formula>`_
on Wikipedia.
.. [6] L. F. Shampine, M. W. Reichelt, "THE MATLAB ODE SUITE", SIAM J. SCI.
COMPUTE., Vol. 18, No. 1, pp. 1-22, January 1997.
.. [7] A. C. Hindmarsh, "ODEPACK, A Systematized Collection of ODE
Solvers," IMACS Transactions on Scientific Computation, Vol 1.,
pp. 55-64, 1983.
.. [8] L. Petzold, "Automatic selection of methods for solving stiff and
nonstiff systems of ordinary differential equations", SIAM Journal
on Scientific and Statistical Computing, Vol. 4, No. 1, pp. 136-148,
1983.
.. [9] `Stiff equation <https://en.wikipedia.org/wiki/Stiff_equation>`_ on
Wikipedia.
.. [10] A. Curtis, M. J. D. Powell, and J. Reid, "On the estimation of
sparse Jacobian matrices", Journal of the Institute of Mathematics
and its Applications, 13, pp. 117-120, 1974.
.. [11] `Cauchy-Riemann equations
<https://en.wikipedia.org/wiki/Cauchy-Riemann_equations>`_ on
Wikipedia.
.. [12] `Lotka-Volterra equations
<https://en.wikipedia.org/wiki/Lotka%E2%80%93Volterra_equations>`_
on Wikipedia.
.. [13] E. Hairer, S. P. Norsett G. Wanner, "Solving Ordinary Differential
Equations I: Nonstiff Problems", Sec. II.
.. [14] `Page with original Fortran code of DOP853
<http://www.unige.ch/~hairer/software.html>`_.
Examples
--------
Basic exponential decay showing automatically chosen time points.
>>> from scipy.integrate import solve_ivp
>>> def exponential_decay(t, y): return -0.5 * y
>>> sol = solve_ivp(exponential_decay, [0, 10], [2, 4, 8])
>>> print(sol.t)
[ 0. 0.11487653 1.26364188 3.06061781 4.81611105 6.57445806
8.33328988 10. ]
>>> print(sol.y)
[[2. 1.88836035 1.06327177 0.43319312 0.18017253 0.07483045
0.03107158 0.01350781]
[4. 3.7767207 2.12654355 0.86638624 0.36034507 0.14966091
0.06214316 0.02701561]
[8. 7.5534414 4.25308709 1.73277247 0.72069014 0.29932181
0.12428631 0.05403123]]
Specifying points where the solution is desired.
>>> sol = solve_ivp(exponential_decay, [0, 10], [2, 4, 8],
... t_eval=[0, 1, 2, 4, 10])
>>> print(sol.t)
[ 0 1 2 4 10]
>>> print(sol.y)
[[2. 1.21305369 0.73534021 0.27066736 0.01350938]
[4. 2.42610739 1.47068043 0.54133472 0.02701876]
[8. 4.85221478 2.94136085 1.08266944 0.05403753]]
Cannon fired upward with terminal event upon impact. The ``terminal`` and
``direction`` fields of an event are applied by monkey patching a function.
Here ``y[0]`` is position and ``y[1]`` is velocity. The projectile starts
at position 0 with velocity +10. Note that the integration never reaches
t=100 because the event is terminal.
>>> def upward_cannon(t, y): return [y[1], -0.5]
>>> def hit_ground(t, y): return y[0]
>>> hit_ground.terminal = True
>>> hit_ground.direction = -1
>>> sol = solve_ivp(upward_cannon, [0, 100], [0, 10], events=hit_ground)
>>> print(sol.t_events)
[array([40.])]
>>> print(sol.t)
[0.00000000e+00 9.99900010e-05 1.09989001e-03 1.10988901e-02
1.11088891e-01 1.11098890e+00 1.11099890e+01 4.00000000e+01]
Use `dense_output` and `events` to find position, which is 100, at the apex
of the cannonball's trajectory. Apex is not defined as terminal, so both
apex and hit_ground are found. There is no information at t=20, so the sol
attribute is used to evaluate the solution. The sol attribute is returned
by setting ``dense_output=True``. Alternatively, the `y_events` attribute
can be used to access the solution at the time of the event.
>>> def apex(t, y): return y[1]
>>> sol = solve_ivp(upward_cannon, [0, 100], [0, 10],
... events=(hit_ground, apex), dense_output=True)
>>> print(sol.t_events)
[array([40.]), array([20.])]
>>> print(sol.t)
[0.00000000e+00 9.99900010e-05 1.09989001e-03 1.10988901e-02
1.11088891e-01 1.11098890e+00 1.11099890e+01 4.00000000e+01]
>>> print(sol.sol(sol.t_events[1][0]))
[100. 0.]
>>> print(sol.y_events)
[array([[-5.68434189e-14, -1.00000000e+01]]), array([[1.00000000e+02, 1.77635684e-15]])]
As an example of a system with additional parameters, we'll implement
the Lotka-Volterra equations [12]_.
>>> def lotkavolterra(t, z, a, b, c, d):
... x, y = z
... return [a*x - b*x*y, -c*y + d*x*y]
...
We pass in the parameter values a=1.5, b=1, c=3 and d=1 with the `args`
argument.
>>> sol = solve_ivp(lotkavolterra, [0, 15], [10, 5], args=(1.5, 1, 3, 1),
... dense_output=True)
Compute a dense solution and plot it.
>>> t = np.linspace(0, 15, 300)
>>> z = sol.sol(t)
>>> import matplotlib.pyplot as plt
>>> plt.plot(t, z.T)
>>> plt.xlabel('t')
>>> plt.legend(['x', 'y'], shadow=True)
>>> plt.title('Lotka-Volterra System')
>>> plt.show()
"""
if method not in METHODS and not (
inspect.isclass(method) and issubclass(method, OdeSolver)):
raise ValueError("`method` must be one of {} or OdeSolver class."
.format(METHODS))
t0, tf = float(t_span[0]), float(t_span[1])
if args is not None:
# Wrap the user's fun (and jac, if given) in lambdas to hide the
# additional parameters. Pass in the original fun as a keyword
# argument to keep it in the scope of the lambda.
fun = lambda t, x, fun=fun: fun(t, x, *args)
jac = options.get('jac')
if callable(jac):
options['jac'] = lambda t, x: jac(t, x, *args)
if t_eval is not None:
t_eval = np.asarray(t_eval)
if t_eval.ndim != 1:
raise ValueError("`t_eval` must be 1-dimensional.")
if np.any(t_eval < min(t0, tf)) or np.any(t_eval > max(t0, tf)):
raise ValueError("Values in `t_eval` are not within `t_span`.")
d = np.diff(t_eval)
if tf > t0 and np.any(d <= 0) or tf < t0 and np.any(d >= 0):
raise ValueError("Values in `t_eval` are not properly sorted.")
if tf > t0:
t_eval_i = 0
else:
# Make order of t_eval decreasing to use np.searchsorted.
t_eval = t_eval[::-1]
# This will be an upper bound for slices.
t_eval_i = t_eval.shape[0]
if method in METHODS:
method = METHODS[method]
solver = method(fun, t0, y0, tf, vectorized=vectorized, **options)
if t_eval is None:
ts = [t0]
ys = [y0]
elif t_eval is not None and dense_output:
ts = []
ti = [t0]
ys = []
else:
ts = []
ys = []
interpolants = []
events, is_terminal, event_dir = prepare_events(events)
if events is not None:
if args is not None:
# Wrap user functions in lambdas to hide the additional parameters.
# The original event function is passed as a keyword argument to the
# lambda to keep the original function in scope (i.e., avoid the
# late binding closure "gotcha").
events = [lambda t, x, event=event: event(t, x, *args)
for event in events]
g = [event(t0, y0) for event in events]
t_events = [[] for _ in range(len(events))]
y_events = [[] for _ in range(len(events))]
else:
t_events = None
y_events = None
status = None
while status is None:
message = solver.step()
if solver.status == 'finished':
status = 0
elif solver.status == 'failed':
status = -1
break
t_old = solver.t_old
t = solver.t
y = solver.y
if dense_output:
sol = solver.dense_output()
interpolants.append(sol)
else:
sol = None
if events is not None:
g_new = [event(t, y) for event in events]
active_events = find_active_events(g, g_new, event_dir)
if active_events.size > 0:
if sol is None:
sol = solver.dense_output()
root_indices, roots, terminate = handle_events(
sol, events, active_events, is_terminal, t_old, t)
for e, te in zip(root_indices, roots):
t_events[e].append(te)
y_events[e].append(sol(te))
if terminate:
status = 1
t = roots[-1]
y = sol(t)
g = g_new
if t_eval is None:
ts.append(t)
ys.append(y)
else:
# The value in t_eval equal to t will be included.
if solver.direction > 0:
t_eval_i_new = np.searchsorted(t_eval, t, side='right')
t_eval_step = t_eval[t_eval_i:t_eval_i_new]
else:
t_eval_i_new = np.searchsorted(t_eval, t, side='left')
# It has to be done with two slice operations, because
# you can't slice to 0th element inclusive using backward
# slicing.
t_eval_step = t_eval[t_eval_i_new:t_eval_i][::-1]
if t_eval_step.size > 0:
if sol is None:
sol = solver.dense_output()
ts.append(t_eval_step)
ys.append(sol(t_eval_step))
t_eval_i = t_eval_i_new
if t_eval is not None and dense_output:
ti.append(t)
message = MESSAGES.get(status, message)
if t_events is not None:
t_events = [np.asarray(te) for te in t_events]
y_events = [np.asarray(ye) for ye in y_events]
if t_eval is None:
ts = np.array(ts)
ys = np.vstack(ys).T
else:
ts = np.hstack(ts)
ys = np.hstack(ys)
if dense_output:
if t_eval is None:
sol = OdeSolution(ts, interpolants)
else:
sol = OdeSolution(ti, interpolants)
else:
sol = None
return OdeResult(t=ts, y=ys, sol=sol, t_events=t_events, y_events=y_events,
nfev=solver.nfev, njev=solver.njev, nlu=solver.nlu,
status=status, message=message, success=status >= 0)

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import numpy as np
from scipy.integrate import ode
from .common import validate_tol, validate_first_step, warn_extraneous
from .base import OdeSolver, DenseOutput
class LSODA(OdeSolver):
"""Adams/BDF method with automatic stiffness detection and switching.
This is a wrapper to the Fortran solver from ODEPACK [1]_. It switches
automatically between the nonstiff Adams method and the stiff BDF method.
The method was originally detailed in [2]_.
Parameters
----------
fun : callable
Right-hand side of the system. The calling signature is ``fun(t, y)``.
Here ``t`` is a scalar, and there are two options for the ndarray ``y``:
It can either have shape (n,); then ``fun`` must return array_like with
shape (n,). Alternatively it can have shape (n, k); then ``fun``
must return an array_like with shape (n, k), i.e. each column
corresponds to a single column in ``y``. The choice between the two
options is determined by `vectorized` argument (see below). The
vectorized implementation allows a faster approximation of the Jacobian
by finite differences (required for this solver).
t0 : float
Initial time.
y0 : array_like, shape (n,)
Initial state.
t_bound : float
Boundary time - the integration won't continue beyond it. It also
determines the direction of the integration.
first_step : float or None, optional
Initial step size. Default is ``None`` which means that the algorithm
should choose.
min_step : float, optional
Minimum allowed step size. Default is 0.0, i.e., the step size is not
bounded and determined solely by the solver.
max_step : float, optional
Maximum allowed step size. Default is np.inf, i.e., the step size is not
bounded and determined solely by the solver.
rtol, atol : float and array_like, optional
Relative and absolute tolerances. The solver keeps the local error
estimates less than ``atol + rtol * abs(y)``. Here `rtol` controls a
relative accuracy (number of correct digits). But if a component of `y`
is approximately below `atol`, the error only needs to fall within
the same `atol` threshold, and the number of correct digits is not
guaranteed. If components of y have different scales, it might be
beneficial to set different `atol` values for different components by
passing array_like with shape (n,) for `atol`. Default values are
1e-3 for `rtol` and 1e-6 for `atol`.
jac : None or callable, optional
Jacobian matrix of the right-hand side of the system with respect to
``y``. The Jacobian matrix has shape (n, n) and its element (i, j) is
equal to ``d f_i / d y_j``. The function will be called as
``jac(t, y)``. If None (default), the Jacobian will be
approximated by finite differences. It is generally recommended to
provide the Jacobian rather than relying on a finite-difference
approximation.
lband, uband : int or None
Parameters defining the bandwidth of the Jacobian,
i.e., ``jac[i, j] != 0 only for i - lband <= j <= i + uband``. Setting
these requires your jac routine to return the Jacobian in the packed format:
the returned array must have ``n`` columns and ``uband + lband + 1``
rows in which Jacobian diagonals are written. Specifically
``jac_packed[uband + i - j , j] = jac[i, j]``. The same format is used
in `scipy.linalg.solve_banded` (check for an illustration).
These parameters can be also used with ``jac=None`` to reduce the
number of Jacobian elements estimated by finite differences.
vectorized : bool, optional
Whether `fun` is implemented in a vectorized fashion. A vectorized
implementation offers no advantages for this solver. Default is False.
Attributes
----------
n : int
Number of equations.
status : string
Current status of the solver: 'running', 'finished' or 'failed'.
t_bound : float
Boundary time.
direction : float
Integration direction: +1 or -1.
t : float
Current time.
y : ndarray
Current state.
t_old : float
Previous time. None if no steps were made yet.
nfev : int
Number of evaluations of the right-hand side.
njev : int
Number of evaluations of the Jacobian.
References
----------
.. [1] A. C. Hindmarsh, "ODEPACK, A Systematized Collection of ODE
Solvers," IMACS Transactions on Scientific Computation, Vol 1.,
pp. 55-64, 1983.
.. [2] L. Petzold, "Automatic selection of methods for solving stiff and
nonstiff systems of ordinary differential equations", SIAM Journal
on Scientific and Statistical Computing, Vol. 4, No. 1, pp. 136-148,
1983.
"""
def __init__(self, fun, t0, y0, t_bound, first_step=None, min_step=0.0,
max_step=np.inf, rtol=1e-3, atol=1e-6, jac=None, lband=None,
uband=None, vectorized=False, **extraneous):
warn_extraneous(extraneous)
super(LSODA, self).__init__(fun, t0, y0, t_bound, vectorized)
if first_step is None:
first_step = 0 # LSODA value for automatic selection.
else:
first_step = validate_first_step(first_step, t0, t_bound)
first_step *= self.direction
if max_step == np.inf:
max_step = 0 # LSODA value for infinity.
elif max_step <= 0:
raise ValueError("`max_step` must be positive.")
if min_step < 0:
raise ValueError("`min_step` must be nonnegative.")
rtol, atol = validate_tol(rtol, atol, self.n)
solver = ode(self.fun, jac)
solver.set_integrator('lsoda', rtol=rtol, atol=atol, max_step=max_step,
min_step=min_step, first_step=first_step,
lband=lband, uband=uband)
solver.set_initial_value(y0, t0)
# Inject t_bound into rwork array as needed for itask=5.
solver._integrator.rwork[0] = self.t_bound
solver._integrator.call_args[4] = solver._integrator.rwork
self._lsoda_solver = solver
def _step_impl(self):
solver = self._lsoda_solver
integrator = solver._integrator
# From lsoda.step and lsoda.integrate itask=5 means take a single
# step and do not go past t_bound.
itask = integrator.call_args[2]
integrator.call_args[2] = 5
solver._y, solver.t = integrator.run(
solver.f, solver.jac or (lambda: None), solver._y, solver.t,
self.t_bound, solver.f_params, solver.jac_params)
integrator.call_args[2] = itask
if solver.successful():
self.t = solver.t
self.y = solver._y
# From LSODA Fortran source njev is equal to nlu.
self.njev = integrator.iwork[12]
self.nlu = integrator.iwork[12]
return True, None
else:
return False, 'Unexpected istate in LSODA.'
def _dense_output_impl(self):
iwork = self._lsoda_solver._integrator.iwork
rwork = self._lsoda_solver._integrator.rwork
order = iwork[14]
h = rwork[11]
yh = np.reshape(rwork[20:20 + (order + 1) * self.n],
(self.n, order + 1), order='F').copy()
return LsodaDenseOutput(self.t_old, self.t, h, order, yh)
class LsodaDenseOutput(DenseOutput):
def __init__(self, t_old, t, h, order, yh):
super(LsodaDenseOutput, self).__init__(t_old, t)
self.h = h
self.yh = yh
self.p = np.arange(order + 1)
def _call_impl(self, t):
if t.ndim == 0:
x = ((t - self.t) / self.h) ** self.p
else:
x = ((t - self.t) / self.h) ** self.p[:, None]
return np.dot(self.yh, x)

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import numpy as np
from scipy.linalg import lu_factor, lu_solve
from scipy.sparse import csc_matrix, issparse, eye
from scipy.sparse.linalg import splu
from scipy.optimize._numdiff import group_columns
from .common import (validate_max_step, validate_tol, select_initial_step,
norm, num_jac, EPS, warn_extraneous,
validate_first_step)
from .base import OdeSolver, DenseOutput
S6 = 6 ** 0.5
# Butcher tableau. A is not used directly, see below.
C = np.array([(4 - S6) / 10, (4 + S6) / 10, 1])
E = np.array([-13 - 7 * S6, -13 + 7 * S6, -1]) / 3
# Eigendecomposition of A is done: A = T L T**-1. There is 1 real eigenvalue
# and a complex conjugate pair. They are written below.
MU_REAL = 3 + 3 ** (2 / 3) - 3 ** (1 / 3)
MU_COMPLEX = (3 + 0.5 * (3 ** (1 / 3) - 3 ** (2 / 3))
- 0.5j * (3 ** (5 / 6) + 3 ** (7 / 6)))
# These are transformation matrices.
T = np.array([
[0.09443876248897524, -0.14125529502095421, 0.03002919410514742],
[0.25021312296533332, 0.20412935229379994, -0.38294211275726192],
[1, 1, 0]])
TI = np.array([
[4.17871859155190428, 0.32768282076106237, 0.52337644549944951],
[-4.17871859155190428, -0.32768282076106237, 0.47662355450055044],
[0.50287263494578682, -2.57192694985560522, 0.59603920482822492]])
# These linear combinations are used in the algorithm.
TI_REAL = TI[0]
TI_COMPLEX = TI[1] + 1j * TI[2]
# Interpolator coefficients.
P = np.array([
[13/3 + 7*S6/3, -23/3 - 22*S6/3, 10/3 + 5 * S6],
[13/3 - 7*S6/3, -23/3 + 22*S6/3, 10/3 - 5 * S6],
[1/3, -8/3, 10/3]])
NEWTON_MAXITER = 6 # Maximum number of Newton iterations.
MIN_FACTOR = 0.2 # Minimum allowed decrease in a step size.
MAX_FACTOR = 10 # Maximum allowed increase in a step size.
def solve_collocation_system(fun, t, y, h, Z0, scale, tol,
LU_real, LU_complex, solve_lu):
"""Solve the collocation system.
Parameters
----------
fun : callable
Right-hand side of the system.
t : float
Current time.
y : ndarray, shape (n,)
Current state.
h : float
Step to try.
Z0 : ndarray, shape (3, n)
Initial guess for the solution. It determines new values of `y` at
``t + h * C`` as ``y + Z0``, where ``C`` is the Radau method constants.
scale : float
Problem tolerance scale, i.e. ``rtol * abs(y) + atol``.
tol : float
Tolerance to which solve the system. This value is compared with
the normalized by `scale` error.
LU_real, LU_complex
LU decompositions of the system Jacobians.
solve_lu : callable
Callable which solves a linear system given a LU decomposition. The
signature is ``solve_lu(LU, b)``.
Returns
-------
converged : bool
Whether iterations converged.
n_iter : int
Number of completed iterations.
Z : ndarray, shape (3, n)
Found solution.
rate : float
The rate of convergence.
"""
n = y.shape[0]
M_real = MU_REAL / h
M_complex = MU_COMPLEX / h
W = TI.dot(Z0)
Z = Z0
F = np.empty((3, n))
ch = h * C
dW_norm_old = None
dW = np.empty_like(W)
converged = False
rate = None
for k in range(NEWTON_MAXITER):
for i in range(3):
F[i] = fun(t + ch[i], y + Z[i])
if not np.all(np.isfinite(F)):
break
f_real = F.T.dot(TI_REAL) - M_real * W[0]
f_complex = F.T.dot(TI_COMPLEX) - M_complex * (W[1] + 1j * W[2])
dW_real = solve_lu(LU_real, f_real)
dW_complex = solve_lu(LU_complex, f_complex)
dW[0] = dW_real
dW[1] = dW_complex.real
dW[2] = dW_complex.imag
dW_norm = norm(dW / scale)
if dW_norm_old is not None:
rate = dW_norm / dW_norm_old
if (rate is not None and (rate >= 1 or
rate ** (NEWTON_MAXITER - k) / (1 - rate) * dW_norm > tol)):
break
W += dW
Z = T.dot(W)
if (dW_norm == 0 or
rate is not None and rate / (1 - rate) * dW_norm < tol):
converged = True
break
dW_norm_old = dW_norm
return converged, k + 1, Z, rate
def predict_factor(h_abs, h_abs_old, error_norm, error_norm_old):
"""Predict by which factor to increase/decrease the step size.
The algorithm is described in [1]_.
Parameters
----------
h_abs, h_abs_old : float
Current and previous values of the step size, `h_abs_old` can be None
(see Notes).
error_norm, error_norm_old : float
Current and previous values of the error norm, `error_norm_old` can
be None (see Notes).
Returns
-------
factor : float
Predicted factor.
Notes
-----
If `h_abs_old` and `error_norm_old` are both not None then a two-step
algorithm is used, otherwise a one-step algorithm is used.
References
----------
.. [1] E. Hairer, S. P. Norsett G. Wanner, "Solving Ordinary Differential
Equations II: Stiff and Differential-Algebraic Problems", Sec. IV.8.
"""
if error_norm_old is None or h_abs_old is None or error_norm == 0:
multiplier = 1
else:
multiplier = h_abs / h_abs_old * (error_norm_old / error_norm) ** 0.25
with np.errstate(divide='ignore'):
factor = min(1, multiplier) * error_norm ** -0.25
return factor
class Radau(OdeSolver):
"""Implicit Runge-Kutta method of Radau IIA family of order 5.
The implementation follows [1]_. The error is controlled with a
third-order accurate embedded formula. A cubic polynomial which satisfies
the collocation conditions is used for the dense output.
Parameters
----------
fun : callable
Right-hand side of the system. The calling signature is ``fun(t, y)``.
Here ``t`` is a scalar, and there are two options for the ndarray ``y``:
It can either have shape (n,); then ``fun`` must return array_like with
shape (n,). Alternatively it can have shape (n, k); then ``fun``
must return an array_like with shape (n, k), i.e., each column
corresponds to a single column in ``y``. The choice between the two
options is determined by `vectorized` argument (see below). The
vectorized implementation allows a faster approximation of the Jacobian
by finite differences (required for this solver).
t0 : float
Initial time.
y0 : array_like, shape (n,)
Initial state.
t_bound : float
Boundary time - the integration won't continue beyond it. It also
determines the direction of the integration.
first_step : float or None, optional
Initial step size. Default is ``None`` which means that the algorithm
should choose.
max_step : float, optional
Maximum allowed step size. Default is np.inf, i.e., the step size is not
bounded and determined solely by the solver.
rtol, atol : float and array_like, optional
Relative and absolute tolerances. The solver keeps the local error
estimates less than ``atol + rtol * abs(y)``. Here `rtol` controls a
relative accuracy (number of correct digits). But if a component of `y`
is approximately below `atol`, the error only needs to fall within
the same `atol` threshold, and the number of correct digits is not
guaranteed. If components of y have different scales, it might be
beneficial to set different `atol` values for different components by
passing array_like with shape (n,) for `atol`. Default values are
1e-3 for `rtol` and 1e-6 for `atol`.
jac : {None, array_like, sparse_matrix, callable}, optional
Jacobian matrix of the right-hand side of the system with respect to
y, required by this method. The Jacobian matrix has shape (n, n) and
its element (i, j) is equal to ``d f_i / d y_j``.
There are three ways to define the Jacobian:
* If array_like or sparse_matrix, the Jacobian is assumed to
be constant.
* If callable, the Jacobian is assumed to depend on both
t and y; it will be called as ``jac(t, y)`` as necessary.
For the 'Radau' and 'BDF' methods, the return value might be a
sparse matrix.
* If None (default), the Jacobian will be approximated by
finite differences.
It is generally recommended to provide the Jacobian rather than
relying on a finite-difference approximation.
jac_sparsity : {None, array_like, sparse matrix}, optional
Defines a sparsity structure of the Jacobian matrix for a
finite-difference approximation. Its shape must be (n, n). This argument
is ignored if `jac` is not `None`. If the Jacobian has only few non-zero
elements in *each* row, providing the sparsity structure will greatly
speed up the computations [2]_. A zero entry means that a corresponding
element in the Jacobian is always zero. If None (default), the Jacobian
is assumed to be dense.
vectorized : bool, optional
Whether `fun` is implemented in a vectorized fashion. Default is False.
Attributes
----------
n : int
Number of equations.
status : string
Current status of the solver: 'running', 'finished' or 'failed'.
t_bound : float
Boundary time.
direction : float
Integration direction: +1 or -1.
t : float
Current time.
y : ndarray
Current state.
t_old : float
Previous time. None if no steps were made yet.
step_size : float
Size of the last successful step. None if no steps were made yet.
nfev : int
Number of evaluations of the right-hand side.
njev : int
Number of evaluations of the Jacobian.
nlu : int
Number of LU decompositions.
References
----------
.. [1] E. Hairer, G. Wanner, "Solving Ordinary Differential Equations II:
Stiff and Differential-Algebraic Problems", Sec. IV.8.
.. [2] A. Curtis, M. J. D. Powell, and J. Reid, "On the estimation of
sparse Jacobian matrices", Journal of the Institute of Mathematics
and its Applications, 13, pp. 117-120, 1974.
"""
def __init__(self, fun, t0, y0, t_bound, max_step=np.inf,
rtol=1e-3, atol=1e-6, jac=None, jac_sparsity=None,
vectorized=False, first_step=None, **extraneous):
warn_extraneous(extraneous)
super(Radau, self).__init__(fun, t0, y0, t_bound, vectorized)
self.y_old = None
self.max_step = validate_max_step(max_step)
self.rtol, self.atol = validate_tol(rtol, atol, self.n)
self.f = self.fun(self.t, self.y)
# Select initial step assuming the same order which is used to control
# the error.
if first_step is None:
self.h_abs = select_initial_step(
self.fun, self.t, self.y, self.f, self.direction,
3, self.rtol, self.atol)
else:
self.h_abs = validate_first_step(first_step, t0, t_bound)
self.h_abs_old = None
self.error_norm_old = None
self.newton_tol = max(10 * EPS / rtol, min(0.03, rtol ** 0.5))
self.sol = None
self.jac_factor = None
self.jac, self.J = self._validate_jac(jac, jac_sparsity)
if issparse(self.J):
def lu(A):
self.nlu += 1
return splu(A)
def solve_lu(LU, b):
return LU.solve(b)
I = eye(self.n, format='csc')
else:
def lu(A):
self.nlu += 1
return lu_factor(A, overwrite_a=True)
def solve_lu(LU, b):
return lu_solve(LU, b, overwrite_b=True)
I = np.identity(self.n)
self.lu = lu
self.solve_lu = solve_lu
self.I = I
self.current_jac = True
self.LU_real = None
self.LU_complex = None
self.Z = None
def _validate_jac(self, jac, sparsity):
t0 = self.t
y0 = self.y
if jac is None:
if sparsity is not None:
if issparse(sparsity):
sparsity = csc_matrix(sparsity)
groups = group_columns(sparsity)
sparsity = (sparsity, groups)
def jac_wrapped(t, y, f):
self.njev += 1
J, self.jac_factor = num_jac(self.fun_vectorized, t, y, f,
self.atol, self.jac_factor,
sparsity)
return J
J = jac_wrapped(t0, y0, self.f)
elif callable(jac):
J = jac(t0, y0)
self.njev = 1
if issparse(J):
J = csc_matrix(J)
def jac_wrapped(t, y, _=None):
self.njev += 1
return csc_matrix(jac(t, y), dtype=float)
else:
J = np.asarray(J, dtype=float)
def jac_wrapped(t, y, _=None):
self.njev += 1
return np.asarray(jac(t, y), dtype=float)
if J.shape != (self.n, self.n):
raise ValueError("`jac` is expected to have shape {}, but "
"actually has {}."
.format((self.n, self.n), J.shape))
else:
if issparse(jac):
J = csc_matrix(jac)
else:
J = np.asarray(jac, dtype=float)
if J.shape != (self.n, self.n):
raise ValueError("`jac` is expected to have shape {}, but "
"actually has {}."
.format((self.n, self.n), J.shape))
jac_wrapped = None
return jac_wrapped, J
def _step_impl(self):
t = self.t
y = self.y
f = self.f
max_step = self.max_step
atol = self.atol
rtol = self.rtol
min_step = 10 * np.abs(np.nextafter(t, self.direction * np.inf) - t)
if self.h_abs > max_step:
h_abs = max_step
h_abs_old = None
error_norm_old = None
elif self.h_abs < min_step:
h_abs = min_step
h_abs_old = None
error_norm_old = None
else:
h_abs = self.h_abs
h_abs_old = self.h_abs_old
error_norm_old = self.error_norm_old
J = self.J
LU_real = self.LU_real
LU_complex = self.LU_complex
current_jac = self.current_jac
jac = self.jac
rejected = False
step_accepted = False
message = None
while not step_accepted:
if h_abs < min_step:
return False, self.TOO_SMALL_STEP
h = h_abs * self.direction
t_new = t + h
if self.direction * (t_new - self.t_bound) > 0:
t_new = self.t_bound
h = t_new - t
h_abs = np.abs(h)
if self.sol is None:
Z0 = np.zeros((3, y.shape[0]))
else:
Z0 = self.sol(t + h * C).T - y
scale = atol + np.abs(y) * rtol
converged = False
while not converged:
if LU_real is None or LU_complex is None:
LU_real = self.lu(MU_REAL / h * self.I - J)
LU_complex = self.lu(MU_COMPLEX / h * self.I - J)
converged, n_iter, Z, rate = solve_collocation_system(
self.fun, t, y, h, Z0, scale, self.newton_tol,
LU_real, LU_complex, self.solve_lu)
if not converged:
if current_jac:
break
J = self.jac(t, y, f)
current_jac = True
LU_real = None
LU_complex = None
if not converged:
h_abs *= 0.5
LU_real = None
LU_complex = None
continue
y_new = y + Z[-1]
ZE = Z.T.dot(E) / h
error = self.solve_lu(LU_real, f + ZE)
scale = atol + np.maximum(np.abs(y), np.abs(y_new)) * rtol
error_norm = norm(error / scale)
safety = 0.9 * (2 * NEWTON_MAXITER + 1) / (2 * NEWTON_MAXITER
+ n_iter)
if rejected and error_norm > 1:
error = self.solve_lu(LU_real, self.fun(t, y + error) + ZE)
error_norm = norm(error / scale)
if error_norm > 1:
factor = predict_factor(h_abs, h_abs_old,
error_norm, error_norm_old)
h_abs *= max(MIN_FACTOR, safety * factor)
LU_real = None
LU_complex = None
rejected = True
else:
step_accepted = True
recompute_jac = jac is not None and n_iter > 2 and rate > 1e-3
factor = predict_factor(h_abs, h_abs_old, error_norm, error_norm_old)
factor = min(MAX_FACTOR, safety * factor)
if not recompute_jac and factor < 1.2:
factor = 1
else:
LU_real = None
LU_complex = None
f_new = self.fun(t_new, y_new)
if recompute_jac:
J = jac(t_new, y_new, f_new)
current_jac = True
elif jac is not None:
current_jac = False
self.h_abs_old = self.h_abs
self.error_norm_old = error_norm
self.h_abs = h_abs * factor
self.y_old = y
self.t = t_new
self.y = y_new
self.f = f_new
self.Z = Z
self.LU_real = LU_real
self.LU_complex = LU_complex
self.current_jac = current_jac
self.J = J
self.t_old = t
self.sol = self._compute_dense_output()
return step_accepted, message
def _compute_dense_output(self):
Q = np.dot(self.Z.T, P)
return RadauDenseOutput(self.t_old, self.t, self.y_old, Q)
def _dense_output_impl(self):
return self.sol
class RadauDenseOutput(DenseOutput):
def __init__(self, t_old, t, y_old, Q):
super(RadauDenseOutput, self).__init__(t_old, t)
self.h = t - t_old
self.Q = Q
self.order = Q.shape[1] - 1
self.y_old = y_old
def _call_impl(self, t):
x = (t - self.t_old) / self.h
if t.ndim == 0:
p = np.tile(x, self.order + 1)
p = np.cumprod(p)
else:
p = np.tile(x, (self.order + 1, 1))
p = np.cumprod(p, axis=0)
# Here we don't multiply by h, not a mistake.
y = np.dot(self.Q, p)
if y.ndim == 2:
y += self.y_old[:, None]
else:
y += self.y_old
return y

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@ -0,0 +1,575 @@
import numpy as np
from .base import OdeSolver, DenseOutput
from .common import (validate_max_step, validate_tol, select_initial_step,
norm, warn_extraneous, validate_first_step)
from . import dop853_coefficients
# Multiply steps computed from asymptotic behaviour of errors by this.
SAFETY = 0.9
MIN_FACTOR = 0.2 # Minimum allowed decrease in a step size.
MAX_FACTOR = 10 # Maximum allowed increase in a step size.
def rk_step(fun, t, y, f, h, A, B, C, K):
"""Perform a single Runge-Kutta step.
This function computes a prediction of an explicit Runge-Kutta method and
also estimates the error of a less accurate method.
Notation for Butcher tableau is as in [1]_.
Parameters
----------
fun : callable
Right-hand side of the system.
t : float
Current time.
y : ndarray, shape (n,)
Current state.
f : ndarray, shape (n,)
Current value of the derivative, i.e., ``fun(x, y)``.
h : float
Step to use.
A : ndarray, shape (n_stages, n_stages)
Coefficients for combining previous RK stages to compute the next
stage. For explicit methods the coefficients at and above the main
diagonal are zeros.
B : ndarray, shape (n_stages,)
Coefficients for combining RK stages for computing the final
prediction.
C : ndarray, shape (n_stages,)
Coefficients for incrementing time for consecutive RK stages.
The value for the first stage is always zero.
K : ndarray, shape (n_stages + 1, n)
Storage array for putting RK stages here. Stages are stored in rows.
The last row is a linear combination of the previous rows with
coefficients
Returns
-------
y_new : ndarray, shape (n,)
Solution at t + h computed with a higher accuracy.
f_new : ndarray, shape (n,)
Derivative ``fun(t + h, y_new)``.
References
----------
.. [1] E. Hairer, S. P. Norsett G. Wanner, "Solving Ordinary Differential
Equations I: Nonstiff Problems", Sec. II.4.
"""
K[0] = f
for s, (a, c) in enumerate(zip(A[1:], C[1:]), start=1):
dy = np.dot(K[:s].T, a[:s]) * h
K[s] = fun(t + c * h, y + dy)
y_new = y + h * np.dot(K[:-1].T, B)
f_new = fun(t + h, y_new)
K[-1] = f_new
return y_new, f_new
class RungeKutta(OdeSolver):
"""Base class for explicit Runge-Kutta methods."""
C = NotImplemented
A = NotImplemented
B = NotImplemented
E = NotImplemented
P = NotImplemented
order = NotImplemented
error_estimator_order = NotImplemented
n_stages = NotImplemented
def __init__(self, fun, t0, y0, t_bound, max_step=np.inf,
rtol=1e-3, atol=1e-6, vectorized=False,
first_step=None, **extraneous):
warn_extraneous(extraneous)
super(RungeKutta, self).__init__(fun, t0, y0, t_bound, vectorized,
support_complex=True)
self.y_old = None
self.max_step = validate_max_step(max_step)
self.rtol, self.atol = validate_tol(rtol, atol, self.n)
self.f = self.fun(self.t, self.y)
if first_step is None:
self.h_abs = select_initial_step(
self.fun, self.t, self.y, self.f, self.direction,
self.error_estimator_order, self.rtol, self.atol)
else:
self.h_abs = validate_first_step(first_step, t0, t_bound)
self.K = np.empty((self.n_stages + 1, self.n), dtype=self.y.dtype)
self.error_exponent = -1 / (self.error_estimator_order + 1)
self.h_previous = None
def _estimate_error(self, K, h):
return np.dot(K.T, self.E) * h
def _estimate_error_norm(self, K, h, scale):
return norm(self._estimate_error(K, h) / scale)
def _step_impl(self):
t = self.t
y = self.y
max_step = self.max_step
rtol = self.rtol
atol = self.atol
min_step = 10 * np.abs(np.nextafter(t, self.direction * np.inf) - t)
if self.h_abs > max_step:
h_abs = max_step
elif self.h_abs < min_step:
h_abs = min_step
else:
h_abs = self.h_abs
step_accepted = False
step_rejected = False
while not step_accepted:
if h_abs < min_step:
return False, self.TOO_SMALL_STEP
h = h_abs * self.direction
t_new = t + h
if self.direction * (t_new - self.t_bound) > 0:
t_new = self.t_bound
h = t_new - t
h_abs = np.abs(h)
y_new, f_new = rk_step(self.fun, t, y, self.f, h, self.A,
self.B, self.C, self.K)
scale = atol + np.maximum(np.abs(y), np.abs(y_new)) * rtol
error_norm = self._estimate_error_norm(self.K, h, scale)
if error_norm < 1:
if error_norm == 0:
factor = MAX_FACTOR
else:
factor = min(MAX_FACTOR,
SAFETY * error_norm ** self.error_exponent)
if step_rejected:
factor = min(1, factor)
h_abs *= factor
step_accepted = True
else:
h_abs *= max(MIN_FACTOR,
SAFETY * error_norm ** self.error_exponent)
step_rejected = True
self.h_previous = h
self.y_old = y
self.t = t_new
self.y = y_new
self.h_abs = h_abs
self.f = f_new
return True, None
def _dense_output_impl(self):
Q = self.K.T.dot(self.P)
return RkDenseOutput(self.t_old, self.t, self.y_old, Q)
class RK23(RungeKutta):
"""Explicit Runge-Kutta method of order 3(2).
This uses the Bogacki-Shampine pair of formulas [1]_. The error is controlled
assuming accuracy of the second-order method, but steps are taken using the
third-order accurate formula (local extrapolation is done). A cubic Hermite
polynomial is used for the dense output.
Can be applied in the complex domain.
Parameters
----------
fun : callable
Right-hand side of the system. The calling signature is ``fun(t, y)``.
Here ``t`` is a scalar and there are two options for ndarray ``y``.
It can either have shape (n,), then ``fun`` must return array_like with
shape (n,). Or alternatively it can have shape (n, k), then ``fun``
must return array_like with shape (n, k), i.e. each column
corresponds to a single column in ``y``. The choice between the two
options is determined by `vectorized` argument (see below).
t0 : float
Initial time.
y0 : array_like, shape (n,)
Initial state.
t_bound : float
Boundary time - the integration won't continue beyond it. It also
determines the direction of the integration.
first_step : float or None, optional
Initial step size. Default is ``None`` which means that the algorithm
should choose.
max_step : float, optional
Maximum allowed step size. Default is np.inf, i.e., the step size is not
bounded and determined solely by the solver.
rtol, atol : float and array_like, optional
Relative and absolute tolerances. The solver keeps the local error
estimates less than ``atol + rtol * abs(y)``. Here, `rtol` controls a
relative accuracy (number of correct digits). But if a component of `y`
is approximately below `atol`, the error only needs to fall within
the same `atol` threshold, and the number of correct digits is not
guaranteed. If components of y have different scales, it might be
beneficial to set different `atol` values for different components by
passing array_like with shape (n,) for `atol`. Default values are
1e-3 for `rtol` and 1e-6 for `atol`.
vectorized : bool, optional
Whether `fun` is implemented in a vectorized fashion. Default is False.
Attributes
----------
n : int
Number of equations.
status : string
Current status of the solver: 'running', 'finished' or 'failed'.
t_bound : float
Boundary time.
direction : float
Integration direction: +1 or -1.
t : float
Current time.
y : ndarray
Current state.
t_old : float
Previous time. None if no steps were made yet.
step_size : float
Size of the last successful step. None if no steps were made yet.
nfev : int
Number evaluations of the system's right-hand side.
njev : int
Number of evaluations of the Jacobian. Is always 0 for this solver as it does not use the Jacobian.
nlu : int
Number of LU decompositions. Is always 0 for this solver.
References
----------
.. [1] P. Bogacki, L.F. Shampine, "A 3(2) Pair of Runge-Kutta Formulas",
Appl. Math. Lett. Vol. 2, No. 4. pp. 321-325, 1989.
"""
order = 3
error_estimator_order = 2
n_stages = 3
C = np.array([0, 1/2, 3/4])
A = np.array([
[0, 0, 0],
[1/2, 0, 0],
[0, 3/4, 0]
])
B = np.array([2/9, 1/3, 4/9])
E = np.array([5/72, -1/12, -1/9, 1/8])
P = np.array([[1, -4 / 3, 5 / 9],
[0, 1, -2/3],
[0, 4/3, -8/9],
[0, -1, 1]])
class RK45(RungeKutta):
"""Explicit Runge-Kutta method of order 5(4).
This uses the Dormand-Prince pair of formulas [1]_. The error is controlled
assuming accuracy of the fourth-order method accuracy, but steps are taken
using the fifth-order accurate formula (local extrapolation is done).
A quartic interpolation polynomial is used for the dense output [2]_.
Can be applied in the complex domain.
Parameters
----------
fun : callable
Right-hand side of the system. The calling signature is ``fun(t, y)``.
Here ``t`` is a scalar, and there are two options for the ndarray ``y``:
It can either have shape (n,); then ``fun`` must return array_like with
shape (n,). Alternatively it can have shape (n, k); then ``fun``
must return an array_like with shape (n, k), i.e., each column
corresponds to a single column in ``y``. The choice between the two
options is determined by `vectorized` argument (see below).
t0 : float
Initial time.
y0 : array_like, shape (n,)
Initial state.
t_bound : float
Boundary time - the integration won't continue beyond it. It also
determines the direction of the integration.
first_step : float or None, optional
Initial step size. Default is ``None`` which means that the algorithm
should choose.
max_step : float, optional
Maximum allowed step size. Default is np.inf, i.e., the step size is not
bounded and determined solely by the solver.
rtol, atol : float and array_like, optional
Relative and absolute tolerances. The solver keeps the local error
estimates less than ``atol + rtol * abs(y)``. Here `rtol` controls a
relative accuracy (number of correct digits). But if a component of `y`
is approximately below `atol`, the error only needs to fall within
the same `atol` threshold, and the number of correct digits is not
guaranteed. If components of y have different scales, it might be
beneficial to set different `atol` values for different components by
passing array_like with shape (n,) for `atol`. Default values are
1e-3 for `rtol` and 1e-6 for `atol`.
vectorized : bool, optional
Whether `fun` is implemented in a vectorized fashion. Default is False.
Attributes
----------
n : int
Number of equations.
status : string
Current status of the solver: 'running', 'finished' or 'failed'.
t_bound : float
Boundary time.
direction : float
Integration direction: +1 or -1.
t : float
Current time.
y : ndarray
Current state.
t_old : float
Previous time. None if no steps were made yet.
step_size : float
Size of the last successful step. None if no steps were made yet.
nfev : int
Number evaluations of the system's right-hand side.
njev : int
Number of evaluations of the Jacobian. Is always 0 for this solver as it does not use the Jacobian.
nlu : int
Number of LU decompositions. Is always 0 for this solver.
References
----------
.. [1] J. R. Dormand, P. J. Prince, "A family of embedded Runge-Kutta
formulae", Journal of Computational and Applied Mathematics, Vol. 6,
No. 1, pp. 19-26, 1980.
.. [2] L. W. Shampine, "Some Practical Runge-Kutta Formulas", Mathematics
of Computation,, Vol. 46, No. 173, pp. 135-150, 1986.
"""
order = 5
error_estimator_order = 4
n_stages = 6
C = np.array([0, 1/5, 3/10, 4/5, 8/9, 1])
A = np.array([
[0, 0, 0, 0, 0],
[1/5, 0, 0, 0, 0],
[3/40, 9/40, 0, 0, 0],
[44/45, -56/15, 32/9, 0, 0],
[19372/6561, -25360/2187, 64448/6561, -212/729, 0],
[9017/3168, -355/33, 46732/5247, 49/176, -5103/18656]
])
B = np.array([35/384, 0, 500/1113, 125/192, -2187/6784, 11/84])
E = np.array([-71/57600, 0, 71/16695, -71/1920, 17253/339200, -22/525,
1/40])
# Corresponds to the optimum value of c_6 from [2]_.
P = np.array([
[1, -8048581381/2820520608, 8663915743/2820520608,
-12715105075/11282082432],
[0, 0, 0, 0],
[0, 131558114200/32700410799, -68118460800/10900136933,
87487479700/32700410799],
[0, -1754552775/470086768, 14199869525/1410260304,
-10690763975/1880347072],
[0, 127303824393/49829197408, -318862633887/49829197408,
701980252875 / 199316789632],
[0, -282668133/205662961, 2019193451/616988883, -1453857185/822651844],
[0, 40617522/29380423, -110615467/29380423, 69997945/29380423]])
class DOP853(RungeKutta):
"""Explicit Runge-Kutta method of order 8.
This is a Python implementation of "DOP853" algorithm originally written
in Fortran [1]_, [2]_. Note that this is not a literate translation, but
the algorithmic core and coefficients are the same.
Can be applied in the complex domain.
Parameters
----------
fun : callable
Right-hand side of the system. The calling signature is ``fun(t, y)``.
Here, ``t`` is a scalar, and there are two options for the ndarray ``y``:
It can either have shape (n,); then ``fun`` must return array_like with
shape (n,). Alternatively it can have shape (n, k); then ``fun``
must return an array_like with shape (n, k), i.e. each column
corresponds to a single column in ``y``. The choice between the two
options is determined by `vectorized` argument (see below).
t0 : float
Initial time.
y0 : array_like, shape (n,)
Initial state.
t_bound : float
Boundary time - the integration won't continue beyond it. It also
determines the direction of the integration.
first_step : float or None, optional
Initial step size. Default is ``None`` which means that the algorithm
should choose.
max_step : float, optional
Maximum allowed step size. Default is np.inf, i.e. the step size is not
bounded and determined solely by the solver.
rtol, atol : float and array_like, optional
Relative and absolute tolerances. The solver keeps the local error
estimates less than ``atol + rtol * abs(y)``. Here `rtol` controls a
relative accuracy (number of correct digits). But if a component of `y`
is approximately below `atol`, the error only needs to fall within
the same `atol` threshold, and the number of correct digits is not
guaranteed. If components of y have different scales, it might be
beneficial to set different `atol` values for different components by
passing array_like with shape (n,) for `atol`. Default values are
1e-3 for `rtol` and 1e-6 for `atol`.
vectorized : bool, optional
Whether `fun` is implemented in a vectorized fashion. Default is False.
Attributes
----------
n : int
Number of equations.
status : string
Current status of the solver: 'running', 'finished' or 'failed'.
t_bound : float
Boundary time.
direction : float
Integration direction: +1 or -1.
t : float
Current time.
y : ndarray
Current state.
t_old : float
Previous time. None if no steps were made yet.
step_size : float
Size of the last successful step. None if no steps were made yet.
nfev : int
Number evaluations of the system's right-hand side.
njev : int
Number of evaluations of the Jacobian. Is always 0 for this solver
as it does not use the Jacobian.
nlu : int
Number of LU decompositions. Is always 0 for this solver.
References
----------
.. [1] E. Hairer, S. P. Norsett G. Wanner, "Solving Ordinary Differential
Equations I: Nonstiff Problems", Sec. II.
.. [2] `Page with original Fortran code of DOP853
<http://www.unige.ch/~hairer/software.html>`_.
"""
n_stages = dop853_coefficients.N_STAGES
order = 8
error_estimator_order = 7
A = dop853_coefficients.A[:n_stages, :n_stages]
B = dop853_coefficients.B
C = dop853_coefficients.C[:n_stages]
E3 = dop853_coefficients.E3
E5 = dop853_coefficients.E5
D = dop853_coefficients.D
A_EXTRA = dop853_coefficients.A[n_stages + 1:]
C_EXTRA = dop853_coefficients.C[n_stages + 1:]
def __init__(self, fun, t0, y0, t_bound, max_step=np.inf,
rtol=1e-3, atol=1e-6, vectorized=False,
first_step=None, **extraneous):
super(DOP853, self).__init__(fun, t0, y0, t_bound, max_step,
rtol, atol, vectorized, first_step,
**extraneous)
self.K_extended = np.empty((dop853_coefficients.N_STAGES_EXTENDED,
self.n), dtype=self.y.dtype)
self.K = self.K_extended[:self.n_stages + 1]
def _estimate_error(self, K, h): # Left for testing purposes.
err5 = np.dot(K.T, self.E5)
err3 = np.dot(K.T, self.E3)
denom = np.hypot(np.abs(err5), 0.1 * np.abs(err3))
correction_factor = np.ones_like(err5)
mask = denom > 0
correction_factor[mask] = np.abs(err5[mask]) / denom[mask]
return h * err5 * correction_factor
def _estimate_error_norm(self, K, h, scale):
err5 = np.dot(K.T, self.E5) / scale
err3 = np.dot(K.T, self.E3) / scale
err5_norm_2 = np.sum(err5**2)
err3_norm_2 = np.sum(err3**2)
denom = err5_norm_2 + 0.01 * err3_norm_2
return np.abs(h) * err5_norm_2 / np.sqrt(denom * len(scale))
def _dense_output_impl(self):
K = self.K_extended
h = self.h_previous
for s, (a, c) in enumerate(zip(self.A_EXTRA, self.C_EXTRA),
start=self.n_stages + 1):
dy = np.dot(K[:s].T, a[:s]) * h
K[s] = self.fun(self.t_old + c * h, self.y_old + dy)
F = np.empty((dop853_coefficients.INTERPOLATOR_POWER, self.n),
dtype=self.y_old.dtype)
f_old = K[0]
delta_y = self.y - self.y_old
F[0] = delta_y
F[1] = h * f_old - delta_y
F[2] = 2 * delta_y - h * (self.f + f_old)
F[3:] = h * np.dot(self.D, K)
return Dop853DenseOutput(self.t_old, self.t, self.y_old, F)
class RkDenseOutput(DenseOutput):
def __init__(self, t_old, t, y_old, Q):
super(RkDenseOutput, self).__init__(t_old, t)
self.h = t - t_old
self.Q = Q
self.order = Q.shape[1] - 1
self.y_old = y_old
def _call_impl(self, t):
x = (t - self.t_old) / self.h
if t.ndim == 0:
p = np.tile(x, self.order + 1)
p = np.cumprod(p)
else:
p = np.tile(x, (self.order + 1, 1))
p = np.cumprod(p, axis=0)
y = self.h * np.dot(self.Q, p)
if y.ndim == 2:
y += self.y_old[:, None]
else:
y += self.y_old
return y
class Dop853DenseOutput(DenseOutput):
def __init__(self, t_old, t, y_old, F):
super(Dop853DenseOutput, self).__init__(t_old, t)
self.h = t - t_old
self.F = F
self.y_old = y_old
def _call_impl(self, t):
x = (t - self.t_old) / self.h
if t.ndim == 0:
y = np.zeros_like(self.y_old)
else:
x = x[:, None]
y = np.zeros((len(x), len(self.y_old)), dtype=self.y_old.dtype)
for i, f in enumerate(reversed(self.F)):
y += f
if i % 2 == 0:
y *= x
else:
y *= 1 - x
y += self.y_old
return y.T

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import sys
import copy
import heapq
import collections
import functools
import numpy as np
from scipy._lib._util import MapWrapper
class LRUDict(collections.OrderedDict):
def __init__(self, max_size):
self.__max_size = max_size
def __setitem__(self, key, value):
existing_key = (key in self)
super(LRUDict, self).__setitem__(key, value)
if existing_key:
self.move_to_end(key)
elif len(self) > self.__max_size:
self.popitem(last=False)
def update(self, other):
# Not needed below
raise NotImplementedError()
class SemiInfiniteFunc(object):
"""
Argument transform from (start, +-oo) to (0, 1)
"""
def __init__(self, func, start, infty):
self._func = func
self._start = start
self._sgn = -1 if infty < 0 else 1
# Overflow threshold for the 1/t**2 factor
self._tmin = sys.float_info.min**0.5
def get_t(self, x):
z = self._sgn * (x - self._start) + 1
if z == 0:
# Can happen only if point not in range
return np.inf
return 1 / z
def __call__(self, t):
if t < self._tmin:
return 0.0
else:
x = self._start + self._sgn * (1 - t) / t
f = self._func(x)
return self._sgn * (f / t) / t
class DoubleInfiniteFunc(object):
"""
Argument transform from (-oo, oo) to (-1, 1)
"""
def __init__(self, func):
self._func = func
# Overflow threshold for the 1/t**2 factor
self._tmin = sys.float_info.min**0.5
def get_t(self, x):
s = -1 if x < 0 else 1
return s / (abs(x) + 1)
def __call__(self, t):
if abs(t) < self._tmin:
return 0.0
else:
x = (1 - abs(t)) / t
f = self._func(x)
return (f / t) / t
def _max_norm(x):
return np.amax(abs(x))
def _get_sizeof(obj):
try:
return sys.getsizeof(obj)
except TypeError:
# occurs on pypy
if hasattr(obj, '__sizeof__'):
return int(obj.__sizeof__())
return 64
class _Bunch(object):
def __init__(self, **kwargs):
self.__keys = kwargs.keys()
self.__dict__.update(**kwargs)
def __repr__(self):
return "_Bunch({})".format(", ".join("{}={}".format(k, repr(self.__dict__[k]))
for k in self.__keys))
def quad_vec(f, a, b, epsabs=1e-200, epsrel=1e-8, norm='2', cache_size=100e6, limit=10000,
workers=1, points=None, quadrature=None, full_output=False):
r"""Adaptive integration of a vector-valued function.
Parameters
----------
f : callable
Vector-valued function f(x) to integrate.
a : float
Initial point.
b : float
Final point.
epsabs : float, optional
Absolute tolerance.
epsrel : float, optional
Relative tolerance.
norm : {'max', '2'}, optional
Vector norm to use for error estimation.
cache_size : int, optional
Number of bytes to use for memoization.
workers : int or map-like callable, optional
If `workers` is an integer, part of the computation is done in
parallel subdivided to this many tasks (using
:class:`python:multiprocessing.pool.Pool`).
Supply `-1` to use all cores available to the Process.
Alternatively, supply a map-like callable, such as
:meth:`python:multiprocessing.pool.Pool.map` for evaluating the
population in parallel.
This evaluation is carried out as ``workers(func, iterable)``.
points : list, optional
List of additional breakpoints.
quadrature : {'gk21', 'gk15', 'trapz'}, optional
Quadrature rule to use on subintervals.
Options: 'gk21' (Gauss-Kronrod 21-point rule),
'gk15' (Gauss-Kronrod 15-point rule),
'trapz' (composite trapezoid rule).
Default: 'gk21' for finite intervals and 'gk15' for (semi-)infinite
full_output : bool, optional
Return an additional ``info`` dictionary.
Returns
-------
res : {float, array-like}
Estimate for the result
err : float
Error estimate for the result in the given norm
info : dict
Returned only when ``full_output=True``.
Info dictionary. Is an object with the attributes:
success : bool
Whether integration reached target precision.
status : int
Indicator for convergence, success (0),
failure (1), and failure due to rounding error (2).
neval : int
Number of function evaluations.
intervals : ndarray, shape (num_intervals, 2)
Start and end points of subdivision intervals.
integrals : ndarray, shape (num_intervals, ...)
Integral for each interval.
Note that at most ``cache_size`` values are recorded,
and the array may contains *nan* for missing items.
errors : ndarray, shape (num_intervals,)
Estimated integration error for each interval.
Notes
-----
The algorithm mainly follows the implementation of QUADPACK's
DQAG* algorithms, implementing global error control and adaptive
subdivision.
The algorithm here has some differences to the QUADPACK approach:
Instead of subdividing one interval at a time, the algorithm
subdivides N intervals with largest errors at once. This enables
(partial) parallelization of the integration.
The logic of subdividing "next largest" intervals first is then
not implemented, and we rely on the above extension to avoid
concentrating on "small" intervals only.
The Wynn epsilon table extrapolation is not used (QUADPACK uses it
for infinite intervals). This is because the algorithm here is
supposed to work on vector-valued functions, in an user-specified
norm, and the extension of the epsilon algorithm to this case does
not appear to be widely agreed. For max-norm, using elementwise
Wynn epsilon could be possible, but we do not do this here with
the hope that the epsilon extrapolation is mainly useful in
special cases.
References
----------
[1] R. Piessens, E. de Doncker, QUADPACK (1983).
Examples
--------
We can compute integrations of a vector-valued function:
>>> from scipy.integrate import quad_vec
>>> import matplotlib.pyplot as plt
>>> alpha = np.linspace(0.0, 2.0, num=30)
>>> f = lambda x: x**alpha
>>> x0, x1 = 0, 2
>>> y, err = quad_vec(f, x0, x1)
>>> plt.plot(alpha, y)
>>> plt.xlabel(r"$\alpha$")
>>> plt.ylabel(r"$\int_{0}^{2} x^\alpha dx$")
>>> plt.show()
"""
a = float(a)
b = float(b)
# Use simple transformations to deal with integrals over infinite
# intervals.
kwargs = dict(epsabs=epsabs,
epsrel=epsrel,
norm=norm,
cache_size=cache_size,
limit=limit,
workers=workers,
points=points,
quadrature='gk15' if quadrature is None else quadrature,
full_output=full_output)
if np.isfinite(a) and np.isinf(b):
f2 = SemiInfiniteFunc(f, start=a, infty=b)
if points is not None:
kwargs['points'] = tuple(f2.get_t(xp) for xp in points)
return quad_vec(f2, 0, 1, **kwargs)
elif np.isfinite(b) and np.isinf(a):
f2 = SemiInfiniteFunc(f, start=b, infty=a)
if points is not None:
kwargs['points'] = tuple(f2.get_t(xp) for xp in points)
res = quad_vec(f2, 0, 1, **kwargs)
return (-res[0],) + res[1:]
elif np.isinf(a) and np.isinf(b):
sgn = -1 if b < a else 1
# NB. explicitly split integral at t=0, which separates
# the positive and negative sides
f2 = DoubleInfiniteFunc(f)
if points is not None:
kwargs['points'] = (0,) + tuple(f2.get_t(xp) for xp in points)
else:
kwargs['points'] = (0,)
if a != b:
res = quad_vec(f2, -1, 1, **kwargs)
else:
res = quad_vec(f2, 1, 1, **kwargs)
return (res[0]*sgn,) + res[1:]
elif not (np.isfinite(a) and np.isfinite(b)):
raise ValueError("invalid integration bounds a={}, b={}".format(a, b))
norm_funcs = {
None: _max_norm,
'max': _max_norm,
'2': np.linalg.norm
}
if callable(norm):
norm_func = norm
else:
norm_func = norm_funcs[norm]
mapwrapper = MapWrapper(workers)
parallel_count = 128
min_intervals = 2
try:
_quadrature = {None: _quadrature_gk21,
'gk21': _quadrature_gk21,
'gk15': _quadrature_gk15,
'trapz': _quadrature_trapz}[quadrature]
except KeyError:
raise ValueError("unknown quadrature {!r}".format(quadrature))
# Initial interval set
if points is None:
initial_intervals = [(a, b)]
else:
prev = a
initial_intervals = []
for p in sorted(points):
p = float(p)
if not (a < p < b) or p == prev:
continue
initial_intervals.append((prev, p))
prev = p
initial_intervals.append((prev, b))
global_integral = None
global_error = None
rounding_error = None
interval_cache = None
intervals = []
neval = 0
for x1, x2 in initial_intervals:
ig, err, rnd = _quadrature(x1, x2, f, norm_func)
neval += _quadrature.num_eval
if global_integral is None:
if isinstance(ig, (float, complex)):
# Specialize for scalars
if norm_func in (_max_norm, np.linalg.norm):
norm_func = abs
global_integral = ig
global_error = float(err)
rounding_error = float(rnd)
cache_count = cache_size // _get_sizeof(ig)
interval_cache = LRUDict(cache_count)
else:
global_integral += ig
global_error += err
rounding_error += rnd
interval_cache[(x1, x2)] = copy.copy(ig)
intervals.append((-err, x1, x2))
heapq.heapify(intervals)
CONVERGED = 0
NOT_CONVERGED = 1
ROUNDING_ERROR = 2
NOT_A_NUMBER = 3
status_msg = {
CONVERGED: "Target precision reached.",
NOT_CONVERGED: "Target precision not reached.",
ROUNDING_ERROR: "Target precision could not be reached due to rounding error.",
NOT_A_NUMBER: "Non-finite values encountered."
}
# Process intervals
with mapwrapper:
ier = NOT_CONVERGED
while intervals and len(intervals) < limit:
# Select intervals with largest errors for subdivision
tol = max(epsabs, epsrel*norm_func(global_integral))
to_process = []
err_sum = 0
for j in range(parallel_count):
if not intervals:
break
if j > 0 and err_sum > global_error - tol/8:
# avoid unnecessary parallel splitting
break
interval = heapq.heappop(intervals)
neg_old_err, a, b = interval
old_int = interval_cache.pop((a, b), None)
to_process.append(((-neg_old_err, a, b, old_int), f, norm_func, _quadrature))
err_sum += -neg_old_err
# Subdivide intervals
for dint, derr, dround_err, subint, dneval in mapwrapper(_subdivide_interval, to_process):
neval += dneval
global_integral += dint
global_error += derr
rounding_error += dround_err
for x in subint:
x1, x2, ig, err = x
interval_cache[(x1, x2)] = ig
heapq.heappush(intervals, (-err, x1, x2))
# Termination check
if len(intervals) >= min_intervals:
tol = max(epsabs, epsrel*norm_func(global_integral))
if global_error < tol/8:
ier = CONVERGED
break
if global_error < rounding_error:
ier = ROUNDING_ERROR
break
if not (np.isfinite(global_error) and np.isfinite(rounding_error)):
ier = NOT_A_NUMBER
break
res = global_integral
err = global_error + rounding_error
if full_output:
res_arr = np.asarray(res)
dummy = np.full(res_arr.shape, np.nan, dtype=res_arr.dtype)
integrals = np.array([interval_cache.get((z[1], z[2]), dummy)
for z in intervals], dtype=res_arr.dtype)
errors = np.array([-z[0] for z in intervals])
intervals = np.array([[z[1], z[2]] for z in intervals])
info = _Bunch(neval=neval,
success=(ier == CONVERGED),
status=ier,
message=status_msg[ier],
intervals=intervals,
integrals=integrals,
errors=errors)
return (res, err, info)
else:
return (res, err)
def _subdivide_interval(args):
interval, f, norm_func, _quadrature = args
old_err, a, b, old_int = interval
c = 0.5 * (a + b)
# Left-hand side
if getattr(_quadrature, 'cache_size', 0) > 0:
f = functools.lru_cache(_quadrature.cache_size)(f)
s1, err1, round1 = _quadrature(a, c, f, norm_func)
dneval = _quadrature.num_eval
s2, err2, round2 = _quadrature(c, b, f, norm_func)
dneval += _quadrature.num_eval
if old_int is None:
old_int, _, _ = _quadrature(a, b, f, norm_func)
dneval += _quadrature.num_eval
if getattr(_quadrature, 'cache_size', 0) > 0:
dneval = f.cache_info().misses
dint = s1 + s2 - old_int
derr = err1 + err2 - old_err
dround_err = round1 + round2
subintervals = ((a, c, s1, err1), (c, b, s2, err2))
return dint, derr, dround_err, subintervals, dneval
def _quadrature_trapz(x1, x2, f, norm_func):
"""
Composite trapezoid quadrature
"""
x3 = 0.5*(x1 + x2)
f1 = f(x1)
f2 = f(x2)
f3 = f(x3)
s2 = 0.25 * (x2 - x1) * (f1 + 2*f3 + f2)
round_err = 0.25 * abs(x2 - x1) * (float(norm_func(f1))
+ 2*float(norm_func(f3))
+ float(norm_func(f2))) * 2e-16
s1 = 0.5 * (x2 - x1) * (f1 + f2)
err = 1/3 * float(norm_func(s1 - s2))
return s2, err, round_err
_quadrature_trapz.cache_size = 3 * 3
_quadrature_trapz.num_eval = 3
def _quadrature_gk(a, b, f, norm_func, x, w, v):
"""
Generic Gauss-Kronrod quadrature
"""
fv = [0.0]*len(x)
c = 0.5 * (a + b)
h = 0.5 * (b - a)
# Gauss-Kronrod
s_k = 0.0
s_k_abs = 0.0
for i in range(len(x)):
ff = f(c + h*x[i])
fv[i] = ff
vv = v[i]
# \int f(x)
s_k += vv * ff
# \int |f(x)|
s_k_abs += vv * abs(ff)
# Gauss
s_g = 0.0
for i in range(len(w)):
s_g += w[i] * fv[2*i + 1]
# Quadrature of abs-deviation from average
s_k_dabs = 0.0
y0 = s_k / 2.0
for i in range(len(x)):
# \int |f(x) - y0|
s_k_dabs += v[i] * abs(fv[i] - y0)
# Use similar error estimation as quadpack
err = float(norm_func((s_k - s_g) * h))
dabs = float(norm_func(s_k_dabs * h))
if dabs != 0 and err != 0:
err = dabs * min(1.0, (200 * err / dabs)**1.5)
eps = sys.float_info.epsilon
round_err = float(norm_func(50 * eps * h * s_k_abs))
if round_err > sys.float_info.min:
err = max(err, round_err)
return h * s_k, err, round_err
def _quadrature_gk21(a, b, f, norm_func):
"""
Gauss-Kronrod 21 quadrature with error estimate
"""
# Gauss-Kronrod points
x = (0.995657163025808080735527280689003,
0.973906528517171720077964012084452,
0.930157491355708226001207180059508,
0.865063366688984510732096688423493,
0.780817726586416897063717578345042,
0.679409568299024406234327365114874,
0.562757134668604683339000099272694,
0.433395394129247190799265943165784,
0.294392862701460198131126603103866,
0.148874338981631210884826001129720,
0,
-0.148874338981631210884826001129720,
-0.294392862701460198131126603103866,
-0.433395394129247190799265943165784,
-0.562757134668604683339000099272694,
-0.679409568299024406234327365114874,
-0.780817726586416897063717578345042,
-0.865063366688984510732096688423493,
-0.930157491355708226001207180059508,
-0.973906528517171720077964012084452,
-0.995657163025808080735527280689003)
# 10-point weights
w = (0.066671344308688137593568809893332,
0.149451349150580593145776339657697,
0.219086362515982043995534934228163,
0.269266719309996355091226921569469,
0.295524224714752870173892994651338,
0.295524224714752870173892994651338,
0.269266719309996355091226921569469,
0.219086362515982043995534934228163,
0.149451349150580593145776339657697,
0.066671344308688137593568809893332)
# 21-point weights
v = (0.011694638867371874278064396062192,
0.032558162307964727478818972459390,
0.054755896574351996031381300244580,
0.075039674810919952767043140916190,
0.093125454583697605535065465083366,
0.109387158802297641899210590325805,
0.123491976262065851077958109831074,
0.134709217311473325928054001771707,
0.142775938577060080797094273138717,
0.147739104901338491374841515972068,
0.149445554002916905664936468389821,
0.147739104901338491374841515972068,
0.142775938577060080797094273138717,
0.134709217311473325928054001771707,
0.123491976262065851077958109831074,
0.109387158802297641899210590325805,
0.093125454583697605535065465083366,
0.075039674810919952767043140916190,
0.054755896574351996031381300244580,
0.032558162307964727478818972459390,
0.011694638867371874278064396062192)
return _quadrature_gk(a, b, f, norm_func, x, w, v)
_quadrature_gk21.num_eval = 21
def _quadrature_gk15(a, b, f, norm_func):
"""
Gauss-Kronrod 15 quadrature with error estimate
"""
# Gauss-Kronrod points
x = (0.991455371120812639206854697526329,
0.949107912342758524526189684047851,
0.864864423359769072789712788640926,
0.741531185599394439863864773280788,
0.586087235467691130294144838258730,
0.405845151377397166906606412076961,
0.207784955007898467600689403773245,
0.000000000000000000000000000000000,
-0.207784955007898467600689403773245,
-0.405845151377397166906606412076961,
-0.586087235467691130294144838258730,
-0.741531185599394439863864773280788,
-0.864864423359769072789712788640926,
-0.949107912342758524526189684047851,
-0.991455371120812639206854697526329)
# 7-point weights
w = (0.129484966168869693270611432679082,
0.279705391489276667901467771423780,
0.381830050505118944950369775488975,
0.417959183673469387755102040816327,
0.381830050505118944950369775488975,
0.279705391489276667901467771423780,
0.129484966168869693270611432679082)
# 15-point weights
v = (0.022935322010529224963732008058970,
0.063092092629978553290700663189204,
0.104790010322250183839876322541518,
0.140653259715525918745189590510238,
0.169004726639267902826583426598550,
0.190350578064785409913256402421014,
0.204432940075298892414161999234649,
0.209482141084727828012999174891714,
0.204432940075298892414161999234649,
0.190350578064785409913256402421014,
0.169004726639267902826583426598550,
0.140653259715525918745189590510238,
0.104790010322250183839876322541518,
0.063092092629978553290700663189204,
0.022935322010529224963732008058970)
return _quadrature_gk(a, b, f, norm_func, x, w, v)
_quadrature_gk15.num_eval = 15

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import functools
import numpy as np
import math
import types
import warnings
# trapz is a public function for scipy.integrate,
# even though it's actually a NumPy function.
from numpy import trapz
from scipy.special import roots_legendre
from scipy.special import gammaln
__all__ = ['fixed_quad', 'quadrature', 'romberg', 'trapz', 'simps', 'romb',
'cumtrapz', 'newton_cotes', 'AccuracyWarning']
# Make See Also linking for our local copy work properly
def _copy_func(f):
"""Based on http://stackoverflow.com/a/6528148/190597 (Glenn Maynard)"""
g = types.FunctionType(f.__code__, f.__globals__, name=f.__name__,
argdefs=f.__defaults__, closure=f.__closure__)
g = functools.update_wrapper(g, f)
g.__kwdefaults__ = f.__kwdefaults__
return g
trapz = _copy_func(trapz)
if trapz.__doc__:
trapz.__doc__ = trapz.__doc__.replace('sum, cumsum', 'numpy.cumsum')
class AccuracyWarning(Warning):
pass
def _cached_roots_legendre(n):
"""
Cache roots_legendre results to speed up calls of the fixed_quad
function.
"""
if n in _cached_roots_legendre.cache:
return _cached_roots_legendre.cache[n]
_cached_roots_legendre.cache[n] = roots_legendre(n)
return _cached_roots_legendre.cache[n]
_cached_roots_legendre.cache = dict()
def fixed_quad(func, a, b, args=(), n=5):
"""
Compute a definite integral using fixed-order Gaussian quadrature.
Integrate `func` from `a` to `b` using Gaussian quadrature of
order `n`.
Parameters
----------
func : callable
A Python function or method to integrate (must accept vector inputs).
If integrating a vector-valued function, the returned array must have
shape ``(..., len(x))``.
a : float
Lower limit of integration.
b : float
Upper limit of integration.
args : tuple, optional
Extra arguments to pass to function, if any.
n : int, optional
Order of quadrature integration. Default is 5.
Returns
-------
val : float
Gaussian quadrature approximation to the integral
none : None
Statically returned value of None
See Also
--------
quad : adaptive quadrature using QUADPACK
dblquad : double integrals
tplquad : triple integrals
romberg : adaptive Romberg quadrature
quadrature : adaptive Gaussian quadrature
romb : integrators for sampled data
simps : integrators for sampled data
cumtrapz : cumulative integration for sampled data
ode : ODE integrator
odeint : ODE integrator
Examples
--------
>>> from scipy import integrate
>>> f = lambda x: x**8
>>> integrate.fixed_quad(f, 0.0, 1.0, n=4)
(0.1110884353741496, None)
>>> integrate.fixed_quad(f, 0.0, 1.0, n=5)
(0.11111111111111102, None)
>>> print(1/9.0) # analytical result
0.1111111111111111
>>> integrate.fixed_quad(np.cos, 0.0, np.pi/2, n=4)
(0.9999999771971152, None)
>>> integrate.fixed_quad(np.cos, 0.0, np.pi/2, n=5)
(1.000000000039565, None)
>>> np.sin(np.pi/2)-np.sin(0) # analytical result
1.0
"""
x, w = _cached_roots_legendre(n)
x = np.real(x)
if np.isinf(a) or np.isinf(b):
raise ValueError("Gaussian quadrature is only available for "
"finite limits.")
y = (b-a)*(x+1)/2.0 + a
return (b-a)/2.0 * np.sum(w*func(y, *args), axis=-1), None
def vectorize1(func, args=(), vec_func=False):
"""Vectorize the call to a function.
This is an internal utility function used by `romberg` and
`quadrature` to create a vectorized version of a function.
If `vec_func` is True, the function `func` is assumed to take vector
arguments.
Parameters
----------
func : callable
User defined function.
args : tuple, optional
Extra arguments for the function.
vec_func : bool, optional
True if the function func takes vector arguments.
Returns
-------
vfunc : callable
A function that will take a vector argument and return the
result.
"""
if vec_func:
def vfunc(x):
return func(x, *args)
else:
def vfunc(x):
if np.isscalar(x):
return func(x, *args)
x = np.asarray(x)
# call with first point to get output type
y0 = func(x[0], *args)
n = len(x)
dtype = getattr(y0, 'dtype', type(y0))
output = np.empty((n,), dtype=dtype)
output[0] = y0
for i in range(1, n):
output[i] = func(x[i], *args)
return output
return vfunc
def quadrature(func, a, b, args=(), tol=1.49e-8, rtol=1.49e-8, maxiter=50,
vec_func=True, miniter=1):
"""
Compute a definite integral using fixed-tolerance Gaussian quadrature.
Integrate `func` from `a` to `b` using Gaussian quadrature
with absolute tolerance `tol`.
Parameters
----------
func : function
A Python function or method to integrate.
a : float
Lower limit of integration.
b : float
Upper limit of integration.
args : tuple, optional
Extra arguments to pass to function.
tol, rtol : float, optional
Iteration stops when error between last two iterates is less than
`tol` OR the relative change is less than `rtol`.
maxiter : int, optional
Maximum order of Gaussian quadrature.
vec_func : bool, optional
True or False if func handles arrays as arguments (is
a "vector" function). Default is True.
miniter : int, optional
Minimum order of Gaussian quadrature.
Returns
-------
val : float
Gaussian quadrature approximation (within tolerance) to integral.
err : float
Difference between last two estimates of the integral.
See also
--------
romberg: adaptive Romberg quadrature
fixed_quad: fixed-order Gaussian quadrature
quad: adaptive quadrature using QUADPACK
dblquad: double integrals
tplquad: triple integrals
romb: integrator for sampled data
simps: integrator for sampled data
cumtrapz: cumulative integration for sampled data
ode: ODE integrator
odeint: ODE integrator
Examples
--------
>>> from scipy import integrate
>>> f = lambda x: x**8
>>> integrate.quadrature(f, 0.0, 1.0)
(0.11111111111111106, 4.163336342344337e-17)
>>> print(1/9.0) # analytical result
0.1111111111111111
>>> integrate.quadrature(np.cos, 0.0, np.pi/2)
(0.9999999999999536, 3.9611425250996035e-11)
>>> np.sin(np.pi/2)-np.sin(0) # analytical result
1.0
"""
if not isinstance(args, tuple):
args = (args,)
vfunc = vectorize1(func, args, vec_func=vec_func)
val = np.inf
err = np.inf
maxiter = max(miniter+1, maxiter)
for n in range(miniter, maxiter+1):
newval = fixed_quad(vfunc, a, b, (), n)[0]
err = abs(newval-val)
val = newval
if err < tol or err < rtol*abs(val):
break
else:
warnings.warn(
"maxiter (%d) exceeded. Latest difference = %e" % (maxiter, err),
AccuracyWarning)
return val, err
def tupleset(t, i, value):
l = list(t)
l[i] = value
return tuple(l)
def cumtrapz(y, x=None, dx=1.0, axis=-1, initial=None):
"""
Cumulatively integrate y(x) using the composite trapezoidal rule.
Parameters
----------
y : array_like
Values to integrate.
x : array_like, optional
The coordinate to integrate along. If None (default), use spacing `dx`
between consecutive elements in `y`.
dx : float, optional
Spacing between elements of `y`. Only used if `x` is None.
axis : int, optional
Specifies the axis to cumulate. Default is -1 (last axis).
initial : scalar, optional
If given, insert this value at the beginning of the returned result.
Typically this value should be 0. Default is None, which means no
value at ``x[0]`` is returned and `res` has one element less than `y`
along the axis of integration.
Returns
-------
res : ndarray
The result of cumulative integration of `y` along `axis`.
If `initial` is None, the shape is such that the axis of integration
has one less value than `y`. If `initial` is given, the shape is equal
to that of `y`.
See Also
--------
numpy.cumsum, numpy.cumprod
quad: adaptive quadrature using QUADPACK
romberg: adaptive Romberg quadrature
quadrature: adaptive Gaussian quadrature
fixed_quad: fixed-order Gaussian quadrature
dblquad: double integrals
tplquad: triple integrals
romb: integrators for sampled data
ode: ODE integrators
odeint: ODE integrators
Examples
--------
>>> from scipy import integrate
>>> import matplotlib.pyplot as plt
>>> x = np.linspace(-2, 2, num=20)
>>> y = x
>>> y_int = integrate.cumtrapz(y, x, initial=0)
>>> plt.plot(x, y_int, 'ro', x, y[0] + 0.5 * x**2, 'b-')
>>> plt.show()
"""
y = np.asarray(y)
if x is None:
d = dx
else:
x = np.asarray(x)
if x.ndim == 1:
d = np.diff(x)
# reshape to correct shape
shape = [1] * y.ndim
shape[axis] = -1
d = d.reshape(shape)
elif len(x.shape) != len(y.shape):
raise ValueError("If given, shape of x must be 1-D or the "
"same as y.")
else:
d = np.diff(x, axis=axis)
if d.shape[axis] != y.shape[axis] - 1:
raise ValueError("If given, length of x along axis must be the "
"same as y.")
nd = len(y.shape)
slice1 = tupleset((slice(None),)*nd, axis, slice(1, None))
slice2 = tupleset((slice(None),)*nd, axis, slice(None, -1))
res = np.cumsum(d * (y[slice1] + y[slice2]) / 2.0, axis=axis)
if initial is not None:
if not np.isscalar(initial):
raise ValueError("`initial` parameter should be a scalar.")
shape = list(res.shape)
shape[axis] = 1
res = np.concatenate([np.full(shape, initial, dtype=res.dtype), res],
axis=axis)
return res
def _basic_simps(y, start, stop, x, dx, axis):
nd = len(y.shape)
if start is None:
start = 0
step = 2
slice_all = (slice(None),)*nd
slice0 = tupleset(slice_all, axis, slice(start, stop, step))
slice1 = tupleset(slice_all, axis, slice(start+1, stop+1, step))
slice2 = tupleset(slice_all, axis, slice(start+2, stop+2, step))
if x is None: # Even-spaced Simpson's rule.
result = np.sum(dx/3.0 * (y[slice0]+4*y[slice1]+y[slice2]),
axis=axis)
else:
# Account for possibly different spacings.
# Simpson's rule changes a bit.
h = np.diff(x, axis=axis)
sl0 = tupleset(slice_all, axis, slice(start, stop, step))
sl1 = tupleset(slice_all, axis, slice(start+1, stop+1, step))
h0 = h[sl0]
h1 = h[sl1]
hsum = h0 + h1
hprod = h0 * h1
h0divh1 = h0 / h1
tmp = hsum/6.0 * (y[slice0]*(2-1.0/h0divh1) +
y[slice1]*hsum*hsum/hprod +
y[slice2]*(2-h0divh1))
result = np.sum(tmp, axis=axis)
return result
def simps(y, x=None, dx=1, axis=-1, even='avg'):
"""
Integrate y(x) using samples along the given axis and the composite
Simpson's rule. If x is None, spacing of dx is assumed.
If there are an even number of samples, N, then there are an odd
number of intervals (N-1), but Simpson's rule requires an even number
of intervals. The parameter 'even' controls how this is handled.
Parameters
----------
y : array_like
Array to be integrated.
x : array_like, optional
If given, the points at which `y` is sampled.
dx : int, optional
Spacing of integration points along axis of `x`. Only used when
`x` is None. Default is 1.
axis : int, optional
Axis along which to integrate. Default is the last axis.
even : str {'avg', 'first', 'last'}, optional
'avg' : Average two results:1) use the first N-2 intervals with
a trapezoidal rule on the last interval and 2) use the last
N-2 intervals with a trapezoidal rule on the first interval.
'first' : Use Simpson's rule for the first N-2 intervals with
a trapezoidal rule on the last interval.
'last' : Use Simpson's rule for the last N-2 intervals with a
trapezoidal rule on the first interval.
See Also
--------
quad: adaptive quadrature using QUADPACK
romberg: adaptive Romberg quadrature
quadrature: adaptive Gaussian quadrature
fixed_quad: fixed-order Gaussian quadrature
dblquad: double integrals
tplquad: triple integrals
romb: integrators for sampled data
cumtrapz: cumulative integration for sampled data
ode: ODE integrators
odeint: ODE integrators
Notes
-----
For an odd number of samples that are equally spaced the result is
exact if the function is a polynomial of order 3 or less. If
the samples are not equally spaced, then the result is exact only
if the function is a polynomial of order 2 or less.
Examples
--------
>>> from scipy import integrate
>>> x = np.arange(0, 10)
>>> y = np.arange(0, 10)
>>> integrate.simps(y, x)
40.5
>>> y = np.power(x, 3)
>>> integrate.simps(y, x)
1642.5
>>> integrate.quad(lambda x: x**3, 0, 9)[0]
1640.25
>>> integrate.simps(y, x, even='first')
1644.5
"""
y = np.asarray(y)
nd = len(y.shape)
N = y.shape[axis]
last_dx = dx
first_dx = dx
returnshape = 0
if x is not None:
x = np.asarray(x)
if len(x.shape) == 1:
shapex = [1] * nd
shapex[axis] = x.shape[0]
saveshape = x.shape
returnshape = 1
x = x.reshape(tuple(shapex))
elif len(x.shape) != len(y.shape):
raise ValueError("If given, shape of x must be 1-D or the "
"same as y.")
if x.shape[axis] != N:
raise ValueError("If given, length of x along axis must be the "
"same as y.")
if N % 2 == 0:
val = 0.0
result = 0.0
slice1 = (slice(None),)*nd
slice2 = (slice(None),)*nd
if even not in ['avg', 'last', 'first']:
raise ValueError("Parameter 'even' must be "
"'avg', 'last', or 'first'.")
# Compute using Simpson's rule on first intervals
if even in ['avg', 'first']:
slice1 = tupleset(slice1, axis, -1)
slice2 = tupleset(slice2, axis, -2)
if x is not None:
last_dx = x[slice1] - x[slice2]
val += 0.5*last_dx*(y[slice1]+y[slice2])
result = _basic_simps(y, 0, N-3, x, dx, axis)
# Compute using Simpson's rule on last set of intervals
if even in ['avg', 'last']:
slice1 = tupleset(slice1, axis, 0)
slice2 = tupleset(slice2, axis, 1)
if x is not None:
first_dx = x[tuple(slice2)] - x[tuple(slice1)]
val += 0.5*first_dx*(y[slice2]+y[slice1])
result += _basic_simps(y, 1, N-2, x, dx, axis)
if even == 'avg':
val /= 2.0
result /= 2.0
result = result + val
else:
result = _basic_simps(y, 0, N-2, x, dx, axis)
if returnshape:
x = x.reshape(saveshape)
return result
def romb(y, dx=1.0, axis=-1, show=False):
"""
Romberg integration using samples of a function.
Parameters
----------
y : array_like
A vector of ``2**k + 1`` equally-spaced samples of a function.
dx : float, optional
The sample spacing. Default is 1.
axis : int, optional
The axis along which to integrate. Default is -1 (last axis).
show : bool, optional
When `y` is a single 1-D array, then if this argument is True
print the table showing Richardson extrapolation from the
samples. Default is False.
Returns
-------
romb : ndarray
The integrated result for `axis`.
See also
--------
quad : adaptive quadrature using QUADPACK
romberg : adaptive Romberg quadrature
quadrature : adaptive Gaussian quadrature
fixed_quad : fixed-order Gaussian quadrature
dblquad : double integrals
tplquad : triple integrals
simps : integrators for sampled data
cumtrapz : cumulative integration for sampled data
ode : ODE integrators
odeint : ODE integrators
Examples
--------
>>> from scipy import integrate
>>> x = np.arange(10, 14.25, 0.25)
>>> y = np.arange(3, 12)
>>> integrate.romb(y)
56.0
>>> y = np.sin(np.power(x, 2.5))
>>> integrate.romb(y)
-0.742561336672229
>>> integrate.romb(y, show=True)
Richardson Extrapolation Table for Romberg Integration
====================================================================
-0.81576
4.63862 6.45674
-1.10581 -3.02062 -3.65245
-2.57379 -3.06311 -3.06595 -3.05664
-1.34093 -0.92997 -0.78776 -0.75160 -0.74256
====================================================================
-0.742561336672229
"""
y = np.asarray(y)
nd = len(y.shape)
Nsamps = y.shape[axis]
Ninterv = Nsamps-1
n = 1
k = 0
while n < Ninterv:
n <<= 1
k += 1
if n != Ninterv:
raise ValueError("Number of samples must be one plus a "
"non-negative power of 2.")
R = {}
slice_all = (slice(None),) * nd
slice0 = tupleset(slice_all, axis, 0)
slicem1 = tupleset(slice_all, axis, -1)
h = Ninterv * np.asarray(dx, dtype=float)
R[(0, 0)] = (y[slice0] + y[slicem1])/2.0*h
slice_R = slice_all
start = stop = step = Ninterv
for i in range(1, k+1):
start >>= 1
slice_R = tupleset(slice_R, axis, slice(start, stop, step))
step >>= 1
R[(i, 0)] = 0.5*(R[(i-1, 0)] + h*y[slice_R].sum(axis=axis))
for j in range(1, i+1):
prev = R[(i, j-1)]
R[(i, j)] = prev + (prev-R[(i-1, j-1)]) / ((1 << (2*j))-1)
h /= 2.0
if show:
if not np.isscalar(R[(0, 0)]):
print("*** Printing table only supported for integrals" +
" of a single data set.")
else:
try:
precis = show[0]
except (TypeError, IndexError):
precis = 5
try:
width = show[1]
except (TypeError, IndexError):
width = 8
formstr = "%%%d.%df" % (width, precis)
title = "Richardson Extrapolation Table for Romberg Integration"
print("", title.center(68), "=" * 68, sep="\n", end="\n")
for i in range(k+1):
for j in range(i+1):
print(formstr % R[(i, j)], end=" ")
print()
print("=" * 68)
print()
return R[(k, k)]
# Romberg quadratures for numeric integration.
#
# Written by Scott M. Ransom <ransom@cfa.harvard.edu>
# last revision: 14 Nov 98
#
# Cosmetic changes by Konrad Hinsen <hinsen@cnrs-orleans.fr>
# last revision: 1999-7-21
#
# Adapted to SciPy by Travis Oliphant <oliphant.travis@ieee.org>
# last revision: Dec 2001
def _difftrap(function, interval, numtraps):
"""
Perform part of the trapezoidal rule to integrate a function.
Assume that we had called difftrap with all lower powers-of-2
starting with 1. Calling difftrap only returns the summation
of the new ordinates. It does _not_ multiply by the width
of the trapezoids. This must be performed by the caller.
'function' is the function to evaluate (must accept vector arguments).
'interval' is a sequence with lower and upper limits
of integration.
'numtraps' is the number of trapezoids to use (must be a
power-of-2).
"""
if numtraps <= 0:
raise ValueError("numtraps must be > 0 in difftrap().")
elif numtraps == 1:
return 0.5*(function(interval[0])+function(interval[1]))
else:
numtosum = numtraps/2
h = float(interval[1]-interval[0])/numtosum
lox = interval[0] + 0.5 * h
points = lox + h * np.arange(numtosum)
s = np.sum(function(points), axis=0)
return s
def _romberg_diff(b, c, k):
"""
Compute the differences for the Romberg quadrature corrections.
See Forman Acton's "Real Computing Made Real," p 143.
"""
tmp = 4.0**k
return (tmp * c - b)/(tmp - 1.0)
def _printresmat(function, interval, resmat):
# Print the Romberg result matrix.
i = j = 0
print('Romberg integration of', repr(function), end=' ')
print('from', interval)
print('')
print('%6s %9s %9s' % ('Steps', 'StepSize', 'Results'))
for i in range(len(resmat)):
print('%6d %9f' % (2**i, (interval[1]-interval[0])/(2.**i)), end=' ')
for j in range(i+1):
print('%9f' % (resmat[i][j]), end=' ')
print('')
print('')
print('The final result is', resmat[i][j], end=' ')
print('after', 2**(len(resmat)-1)+1, 'function evaluations.')
def romberg(function, a, b, args=(), tol=1.48e-8, rtol=1.48e-8, show=False,
divmax=10, vec_func=False):
"""
Romberg integration of a callable function or method.
Returns the integral of `function` (a function of one variable)
over the interval (`a`, `b`).
If `show` is 1, the triangular array of the intermediate results
will be printed. If `vec_func` is True (default is False), then
`function` is assumed to support vector arguments.
Parameters
----------
function : callable
Function to be integrated.
a : float
Lower limit of integration.
b : float
Upper limit of integration.
Returns
-------
results : float
Result of the integration.
Other Parameters
----------------
args : tuple, optional
Extra arguments to pass to function. Each element of `args` will
be passed as a single argument to `func`. Default is to pass no
extra arguments.
tol, rtol : float, optional
The desired absolute and relative tolerances. Defaults are 1.48e-8.
show : bool, optional
Whether to print the results. Default is False.
divmax : int, optional
Maximum order of extrapolation. Default is 10.
vec_func : bool, optional
Whether `func` handles arrays as arguments (i.e., whether it is a
"vector" function). Default is False.
See Also
--------
fixed_quad : Fixed-order Gaussian quadrature.
quad : Adaptive quadrature using QUADPACK.
dblquad : Double integrals.
tplquad : Triple integrals.
romb : Integrators for sampled data.
simps : Integrators for sampled data.
cumtrapz : Cumulative integration for sampled data.
ode : ODE integrator.
odeint : ODE integrator.
References
----------
.. [1] 'Romberg's method' https://en.wikipedia.org/wiki/Romberg%27s_method
Examples
--------
Integrate a gaussian from 0 to 1 and compare to the error function.
>>> from scipy import integrate
>>> from scipy.special import erf
>>> gaussian = lambda x: 1/np.sqrt(np.pi) * np.exp(-x**2)
>>> result = integrate.romberg(gaussian, 0, 1, show=True)
Romberg integration of <function vfunc at ...> from [0, 1]
::
Steps StepSize Results
1 1.000000 0.385872
2 0.500000 0.412631 0.421551
4 0.250000 0.419184 0.421368 0.421356
8 0.125000 0.420810 0.421352 0.421350 0.421350
16 0.062500 0.421215 0.421350 0.421350 0.421350 0.421350
32 0.031250 0.421317 0.421350 0.421350 0.421350 0.421350 0.421350
The final result is 0.421350396475 after 33 function evaluations.
>>> print("%g %g" % (2*result, erf(1)))
0.842701 0.842701
"""
if np.isinf(a) or np.isinf(b):
raise ValueError("Romberg integration only available "
"for finite limits.")
vfunc = vectorize1(function, args, vec_func=vec_func)
n = 1
interval = [a, b]
intrange = b - a
ordsum = _difftrap(vfunc, interval, n)
result = intrange * ordsum
resmat = [[result]]
err = np.inf
last_row = resmat[0]
for i in range(1, divmax+1):
n *= 2
ordsum += _difftrap(vfunc, interval, n)
row = [intrange * ordsum / n]
for k in range(i):
row.append(_romberg_diff(last_row[k], row[k], k+1))
result = row[i]
lastresult = last_row[i-1]
if show:
resmat.append(row)
err = abs(result - lastresult)
if err < tol or err < rtol * abs(result):
break
last_row = row
else:
warnings.warn(
"divmax (%d) exceeded. Latest difference = %e" % (divmax, err),
AccuracyWarning)
if show:
_printresmat(vfunc, interval, resmat)
return result
# Coefficients for Newton-Cotes quadrature
#
# These are the points being used
# to construct the local interpolating polynomial
# a are the weights for Newton-Cotes integration
# B is the error coefficient.
# error in these coefficients grows as N gets larger.
# or as samples are closer and closer together
# You can use maxima to find these rational coefficients
# for equally spaced data using the commands
# a(i,N) := integrate(product(r-j,j,0,i-1) * product(r-j,j,i+1,N),r,0,N) / ((N-i)! * i!) * (-1)^(N-i);
# Be(N) := N^(N+2)/(N+2)! * (N/(N+3) - sum((i/N)^(N+2)*a(i,N),i,0,N));
# Bo(N) := N^(N+1)/(N+1)! * (N/(N+2) - sum((i/N)^(N+1)*a(i,N),i,0,N));
# B(N) := (if (mod(N,2)=0) then Be(N) else Bo(N));
#
# pre-computed for equally-spaced weights
#
# num_a, den_a, int_a, num_B, den_B = _builtincoeffs[N]
#
# a = num_a*array(int_a)/den_a
# B = num_B*1.0 / den_B
#
# integrate(f(x),x,x_0,x_N) = dx*sum(a*f(x_i)) + B*(dx)^(2k+3) f^(2k+2)(x*)
# where k = N // 2
#
_builtincoeffs = {
1: (1,2,[1,1],-1,12),
2: (1,3,[1,4,1],-1,90),
3: (3,8,[1,3,3,1],-3,80),
4: (2,45,[7,32,12,32,7],-8,945),
5: (5,288,[19,75,50,50,75,19],-275,12096),
6: (1,140,[41,216,27,272,27,216,41],-9,1400),
7: (7,17280,[751,3577,1323,2989,2989,1323,3577,751],-8183,518400),
8: (4,14175,[989,5888,-928,10496,-4540,10496,-928,5888,989],
-2368,467775),
9: (9,89600,[2857,15741,1080,19344,5778,5778,19344,1080,
15741,2857], -4671, 394240),
10: (5,299376,[16067,106300,-48525,272400,-260550,427368,
-260550,272400,-48525,106300,16067],
-673175, 163459296),
11: (11,87091200,[2171465,13486539,-3237113, 25226685,-9595542,
15493566,15493566,-9595542,25226685,-3237113,
13486539,2171465], -2224234463, 237758976000),
12: (1, 5255250, [1364651,9903168,-7587864,35725120,-51491295,
87516288,-87797136,87516288,-51491295,35725120,
-7587864,9903168,1364651], -3012, 875875),
13: (13, 402361344000,[8181904909, 56280729661, -31268252574,
156074417954,-151659573325,206683437987,
-43111992612,-43111992612,206683437987,
-151659573325,156074417954,-31268252574,
56280729661,8181904909], -2639651053,
344881152000),
14: (7, 2501928000, [90241897,710986864,-770720657,3501442784,
-6625093363,12630121616,-16802270373,19534438464,
-16802270373,12630121616,-6625093363,3501442784,
-770720657,710986864,90241897], -3740727473,
1275983280000)
}
def newton_cotes(rn, equal=0):
r"""
Return weights and error coefficient for Newton-Cotes integration.
Suppose we have (N+1) samples of f at the positions
x_0, x_1, ..., x_N. Then an N-point Newton-Cotes formula for the
integral between x_0 and x_N is:
:math:`\int_{x_0}^{x_N} f(x)dx = \Delta x \sum_{i=0}^{N} a_i f(x_i)
+ B_N (\Delta x)^{N+2} f^{N+1} (\xi)`
where :math:`\xi \in [x_0,x_N]`
and :math:`\Delta x = \frac{x_N-x_0}{N}` is the average samples spacing.
If the samples are equally-spaced and N is even, then the error
term is :math:`B_N (\Delta x)^{N+3} f^{N+2}(\xi)`.
Parameters
----------
rn : int
The integer order for equally-spaced data or the relative positions of
the samples with the first sample at 0 and the last at N, where N+1 is
the length of `rn`. N is the order of the Newton-Cotes integration.
equal : int, optional
Set to 1 to enforce equally spaced data.
Returns
-------
an : ndarray
1-D array of weights to apply to the function at the provided sample
positions.
B : float
Error coefficient.
Examples
--------
Compute the integral of sin(x) in [0, :math:`\pi`]:
>>> from scipy.integrate import newton_cotes
>>> def f(x):
... return np.sin(x)
>>> a = 0
>>> b = np.pi
>>> exact = 2
>>> for N in [2, 4, 6, 8, 10]:
... x = np.linspace(a, b, N + 1)
... an, B = newton_cotes(N, 1)
... dx = (b - a) / N
... quad = dx * np.sum(an * f(x))
... error = abs(quad - exact)
... print('{:2d} {:10.9f} {:.5e}'.format(N, quad, error))
...
2 2.094395102 9.43951e-02
4 1.998570732 1.42927e-03
6 2.000017814 1.78136e-05
8 1.999999835 1.64725e-07
10 2.000000001 1.14677e-09
Notes
-----
Normally, the Newton-Cotes rules are used on smaller integration
regions and a composite rule is used to return the total integral.
"""
try:
N = len(rn)-1
if equal:
rn = np.arange(N+1)
elif np.all(np.diff(rn) == 1):
equal = 1
except Exception:
N = rn
rn = np.arange(N+1)
equal = 1
if equal and N in _builtincoeffs:
na, da, vi, nb, db = _builtincoeffs[N]
an = na * np.array(vi, dtype=float) / da
return an, float(nb)/db
if (rn[0] != 0) or (rn[-1] != N):
raise ValueError("The sample positions must start at 0"
" and end at N")
yi = rn / float(N)
ti = 2 * yi - 1
nvec = np.arange(N+1)
C = ti ** nvec[:, np.newaxis]
Cinv = np.linalg.inv(C)
# improve precision of result
for i in range(2):
Cinv = 2*Cinv - Cinv.dot(C).dot(Cinv)
vec = 2.0 / (nvec[::2]+1)
ai = Cinv[:, ::2].dot(vec) * (N / 2.)
if (N % 2 == 0) and equal:
BN = N/(N+3.)
power = N+2
else:
BN = N/(N+2.)
power = N+1
BN = BN - np.dot(yi**power, ai)
p1 = power+1
fac = power*math.log(N) - gammaln(p1)
fac = math.exp(fac)
return ai, BN*fac

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# Author: Travis Oliphant
__all__ = ['odeint']
import numpy as np
from . import _odepack
from copy import copy
import warnings
class ODEintWarning(Warning):
pass
_msgs = {2: "Integration successful.",
1: "Nothing was done; the integration time was 0.",
-1: "Excess work done on this call (perhaps wrong Dfun type).",
-2: "Excess accuracy requested (tolerances too small).",
-3: "Illegal input detected (internal error).",
-4: "Repeated error test failures (internal error).",
-5: "Repeated convergence failures (perhaps bad Jacobian or tolerances).",
-6: "Error weight became zero during problem.",
-7: "Internal workspace insufficient to finish (internal error).",
-8: "Run terminated (internal error)."
}
def odeint(func, y0, t, args=(), Dfun=None, col_deriv=0, full_output=0,
ml=None, mu=None, rtol=None, atol=None, tcrit=None, h0=0.0,
hmax=0.0, hmin=0.0, ixpr=0, mxstep=0, mxhnil=0, mxordn=12,
mxords=5, printmessg=0, tfirst=False):
"""
Integrate a system of ordinary differential equations.
.. note:: For new code, use `scipy.integrate.solve_ivp` to solve a
differential equation.
Solve a system of ordinary differential equations using lsoda from the
FORTRAN library odepack.
Solves the initial value problem for stiff or non-stiff systems
of first order ode-s::
dy/dt = func(y, t, ...) [or func(t, y, ...)]
where y can be a vector.
.. note:: By default, the required order of the first two arguments of
`func` are in the opposite order of the arguments in the system
definition function used by the `scipy.integrate.ode` class and
the function `scipy.integrate.solve_ivp`. To use a function with
the signature ``func(t, y, ...)``, the argument `tfirst` must be
set to ``True``.
Parameters
----------
func : callable(y, t, ...) or callable(t, y, ...)
Computes the derivative of y at t.
If the signature is ``callable(t, y, ...)``, then the argument
`tfirst` must be set ``True``.
y0 : array
Initial condition on y (can be a vector).
t : array
A sequence of time points for which to solve for y. The initial
value point should be the first element of this sequence.
This sequence must be monotonically increasing or monotonically
decreasing; repeated values are allowed.
args : tuple, optional
Extra arguments to pass to function.
Dfun : callable(y, t, ...) or callable(t, y, ...)
Gradient (Jacobian) of `func`.
If the signature is ``callable(t, y, ...)``, then the argument
`tfirst` must be set ``True``.
col_deriv : bool, optional
True if `Dfun` defines derivatives down columns (faster),
otherwise `Dfun` should define derivatives across rows.
full_output : bool, optional
True if to return a dictionary of optional outputs as the second output
printmessg : bool, optional
Whether to print the convergence message
tfirst: bool, optional
If True, the first two arguments of `func` (and `Dfun`, if given)
must ``t, y`` instead of the default ``y, t``.
.. versionadded:: 1.1.0
Returns
-------
y : array, shape (len(t), len(y0))
Array containing the value of y for each desired time in t,
with the initial value `y0` in the first row.
infodict : dict, only returned if full_output == True
Dictionary containing additional output information
======= ============================================================
key meaning
======= ============================================================
'hu' vector of step sizes successfully used for each time step
'tcur' vector with the value of t reached for each time step
(will always be at least as large as the input times)
'tolsf' vector of tolerance scale factors, greater than 1.0,
computed when a request for too much accuracy was detected
'tsw' value of t at the time of the last method switch
(given for each time step)
'nst' cumulative number of time steps
'nfe' cumulative number of function evaluations for each time step
'nje' cumulative number of jacobian evaluations for each time step
'nqu' a vector of method orders for each successful step
'imxer' index of the component of largest magnitude in the
weighted local error vector (e / ewt) on an error return, -1
otherwise
'lenrw' the length of the double work array required
'leniw' the length of integer work array required
'mused' a vector of method indicators for each successful time step:
1: adams (nonstiff), 2: bdf (stiff)
======= ============================================================
Other Parameters
----------------
ml, mu : int, optional
If either of these are not None or non-negative, then the
Jacobian is assumed to be banded. These give the number of
lower and upper non-zero diagonals in this banded matrix.
For the banded case, `Dfun` should return a matrix whose
rows contain the non-zero bands (starting with the lowest diagonal).
Thus, the return matrix `jac` from `Dfun` should have shape
``(ml + mu + 1, len(y0))`` when ``ml >=0`` or ``mu >=0``.
The data in `jac` must be stored such that ``jac[i - j + mu, j]``
holds the derivative of the `i`th equation with respect to the `j`th
state variable. If `col_deriv` is True, the transpose of this
`jac` must be returned.
rtol, atol : float, optional
The input parameters `rtol` and `atol` determine the error
control performed by the solver. The solver will control the
vector, e, of estimated local errors in y, according to an
inequality of the form ``max-norm of (e / ewt) <= 1``,
where ewt is a vector of positive error weights computed as
``ewt = rtol * abs(y) + atol``.
rtol and atol can be either vectors the same length as y or scalars.
Defaults to 1.49012e-8.
tcrit : ndarray, optional
Vector of critical points (e.g., singularities) where integration
care should be taken.
h0 : float, (0: solver-determined), optional
The step size to be attempted on the first step.
hmax : float, (0: solver-determined), optional
The maximum absolute step size allowed.
hmin : float, (0: solver-determined), optional
The minimum absolute step size allowed.
ixpr : bool, optional
Whether to generate extra printing at method switches.
mxstep : int, (0: solver-determined), optional
Maximum number of (internally defined) steps allowed for each
integration point in t.
mxhnil : int, (0: solver-determined), optional
Maximum number of messages printed.
mxordn : int, (0: solver-determined), optional
Maximum order to be allowed for the non-stiff (Adams) method.
mxords : int, (0: solver-determined), optional
Maximum order to be allowed for the stiff (BDF) method.
See Also
--------
solve_ivp : solve an initial value problem for a system of ODEs
ode : a more object-oriented integrator based on VODE
quad : for finding the area under a curve
Examples
--------
The second order differential equation for the angle `theta` of a
pendulum acted on by gravity with friction can be written::
theta''(t) + b*theta'(t) + c*sin(theta(t)) = 0
where `b` and `c` are positive constants, and a prime (') denotes a
derivative. To solve this equation with `odeint`, we must first convert
it to a system of first order equations. By defining the angular
velocity ``omega(t) = theta'(t)``, we obtain the system::
theta'(t) = omega(t)
omega'(t) = -b*omega(t) - c*sin(theta(t))
Let `y` be the vector [`theta`, `omega`]. We implement this system
in Python as:
>>> def pend(y, t, b, c):
... theta, omega = y
... dydt = [omega, -b*omega - c*np.sin(theta)]
... return dydt
...
We assume the constants are `b` = 0.25 and `c` = 5.0:
>>> b = 0.25
>>> c = 5.0
For initial conditions, we assume the pendulum is nearly vertical
with `theta(0)` = `pi` - 0.1, and is initially at rest, so
`omega(0)` = 0. Then the vector of initial conditions is
>>> y0 = [np.pi - 0.1, 0.0]
We will generate a solution at 101 evenly spaced samples in the interval
0 <= `t` <= 10. So our array of times is:
>>> t = np.linspace(0, 10, 101)
Call `odeint` to generate the solution. To pass the parameters
`b` and `c` to `pend`, we give them to `odeint` using the `args`
argument.
>>> from scipy.integrate import odeint
>>> sol = odeint(pend, y0, t, args=(b, c))
The solution is an array with shape (101, 2). The first column
is `theta(t)`, and the second is `omega(t)`. The following code
plots both components.
>>> import matplotlib.pyplot as plt
>>> plt.plot(t, sol[:, 0], 'b', label='theta(t)')
>>> plt.plot(t, sol[:, 1], 'g', label='omega(t)')
>>> plt.legend(loc='best')
>>> plt.xlabel('t')
>>> plt.grid()
>>> plt.show()
"""
if ml is None:
ml = -1 # changed to zero inside function call
if mu is None:
mu = -1 # changed to zero inside function call
dt = np.diff(t)
if not((dt >= 0).all() or (dt <= 0).all()):
raise ValueError("The values in t must be monotonically increasing "
"or monotonically decreasing; repeated values are "
"allowed.")
t = copy(t)
y0 = copy(y0)
output = _odepack.odeint(func, y0, t, args, Dfun, col_deriv, ml, mu,
full_output, rtol, atol, tcrit, h0, hmax, hmin,
ixpr, mxstep, mxhnil, mxordn, mxords,
int(bool(tfirst)))
if output[-1] < 0:
warning_msg = _msgs[output[-1]] + " Run with full_output = 1 to get quantitative information."
warnings.warn(warning_msg, ODEintWarning)
elif printmessg:
warning_msg = _msgs[output[-1]]
warnings.warn(warning_msg, ODEintWarning)
if full_output:
output[1]['message'] = _msgs[output[-1]]
output = output[:-1]
if len(output) == 1:
return output[0]
else:
return output

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@ -0,0 +1,899 @@
# Author: Travis Oliphant 2001
# Author: Nathan Woods 2013 (nquad &c)
import sys
import warnings
from functools import partial
from . import _quadpack
import numpy
from numpy import Inf
__all__ = ['quad', 'dblquad', 'tplquad', 'nquad', 'quad_explain',
'IntegrationWarning']
error = _quadpack.error
class IntegrationWarning(UserWarning):
"""
Warning on issues during integration.
"""
pass
def quad_explain(output=sys.stdout):
"""
Print extra information about integrate.quad() parameters and returns.
Parameters
----------
output : instance with "write" method, optional
Information about `quad` is passed to ``output.write()``.
Default is ``sys.stdout``.
Returns
-------
None
Examples
--------
We can show detailed information of the `integrate.quad` function in stdout:
>>> from scipy.integrate import quad_explain
>>> quad_explain()
"""
output.write(quad.__doc__)
def quad(func, a, b, args=(), full_output=0, epsabs=1.49e-8, epsrel=1.49e-8,
limit=50, points=None, weight=None, wvar=None, wopts=None, maxp1=50,
limlst=50):
"""
Compute a definite integral.
Integrate func from `a` to `b` (possibly infinite interval) using a
technique from the Fortran library QUADPACK.
Parameters
----------
func : {function, scipy.LowLevelCallable}
A Python function or method to integrate. If `func` takes many
arguments, it is integrated along the axis corresponding to the
first argument.
If the user desires improved integration performance, then `f` may
be a `scipy.LowLevelCallable` with one of the signatures::
double func(double x)
double func(double x, void *user_data)
double func(int n, double *xx)
double func(int n, double *xx, void *user_data)
The ``user_data`` is the data contained in the `scipy.LowLevelCallable`.
In the call forms with ``xx``, ``n`` is the length of the ``xx``
array which contains ``xx[0] == x`` and the rest of the items are
numbers contained in the ``args`` argument of quad.
In addition, certain ctypes call signatures are supported for
backward compatibility, but those should not be used in new code.
a : float
Lower limit of integration (use -numpy.inf for -infinity).
b : float
Upper limit of integration (use numpy.inf for +infinity).
args : tuple, optional
Extra arguments to pass to `func`.
full_output : int, optional
Non-zero to return a dictionary of integration information.
If non-zero, warning messages are also suppressed and the
message is appended to the output tuple.
Returns
-------
y : float
The integral of func from `a` to `b`.
abserr : float
An estimate of the absolute error in the result.
infodict : dict
A dictionary containing additional information.
Run scipy.integrate.quad_explain() for more information.
message
A convergence message.
explain
Appended only with 'cos' or 'sin' weighting and infinite
integration limits, it contains an explanation of the codes in
infodict['ierlst']
Other Parameters
----------------
epsabs : float or int, optional
Absolute error tolerance. Default is 1.49e-8. `quad` tries to obtain
an accuracy of ``abs(i-result) <= max(epsabs, epsrel*abs(i))``
where ``i`` = integral of `func` from `a` to `b`, and ``result`` is the
numerical approximation. See `epsrel` below.
epsrel : float or int, optional
Relative error tolerance. Default is 1.49e-8.
If ``epsabs <= 0``, `epsrel` must be greater than both 5e-29
and ``50 * (machine epsilon)``. See `epsabs` above.
limit : float or int, optional
An upper bound on the number of subintervals used in the adaptive
algorithm.
points : (sequence of floats,ints), optional
A sequence of break points in the bounded integration interval
where local difficulties of the integrand may occur (e.g.,
singularities, discontinuities). The sequence does not have
to be sorted. Note that this option cannot be used in conjunction
with ``weight``.
weight : float or int, optional
String indicating weighting function. Full explanation for this
and the remaining arguments can be found below.
wvar : optional
Variables for use with weighting functions.
wopts : optional
Optional input for reusing Chebyshev moments.
maxp1 : float or int, optional
An upper bound on the number of Chebyshev moments.
limlst : int, optional
Upper bound on the number of cycles (>=3) for use with a sinusoidal
weighting and an infinite end-point.
See Also
--------
dblquad : double integral
tplquad : triple integral
nquad : n-dimensional integrals (uses `quad` recursively)
fixed_quad : fixed-order Gaussian quadrature
quadrature : adaptive Gaussian quadrature
odeint : ODE integrator
ode : ODE integrator
simps : integrator for sampled data
romb : integrator for sampled data
scipy.special : for coefficients and roots of orthogonal polynomials
Notes
-----
**Extra information for quad() inputs and outputs**
If full_output is non-zero, then the third output argument
(infodict) is a dictionary with entries as tabulated below. For
infinite limits, the range is transformed to (0,1) and the
optional outputs are given with respect to this transformed range.
Let M be the input argument limit and let K be infodict['last'].
The entries are:
'neval'
The number of function evaluations.
'last'
The number, K, of subintervals produced in the subdivision process.
'alist'
A rank-1 array of length M, the first K elements of which are the
left end points of the subintervals in the partition of the
integration range.
'blist'
A rank-1 array of length M, the first K elements of which are the
right end points of the subintervals.
'rlist'
A rank-1 array of length M, the first K elements of which are the
integral approximations on the subintervals.
'elist'
A rank-1 array of length M, the first K elements of which are the
moduli of the absolute error estimates on the subintervals.
'iord'
A rank-1 integer array of length M, the first L elements of
which are pointers to the error estimates over the subintervals
with ``L=K`` if ``K<=M/2+2`` or ``L=M+1-K`` otherwise. Let I be the
sequence ``infodict['iord']`` and let E be the sequence
``infodict['elist']``. Then ``E[I[1]], ..., E[I[L]]`` forms a
decreasing sequence.
If the input argument points is provided (i.e., it is not None),
the following additional outputs are placed in the output
dictionary. Assume the points sequence is of length P.
'pts'
A rank-1 array of length P+2 containing the integration limits
and the break points of the intervals in ascending order.
This is an array giving the subintervals over which integration
will occur.
'level'
A rank-1 integer array of length M (=limit), containing the
subdivision levels of the subintervals, i.e., if (aa,bb) is a
subinterval of ``(pts[1], pts[2])`` where ``pts[0]`` and ``pts[2]``
are adjacent elements of ``infodict['pts']``, then (aa,bb) has level l
if ``|bb-aa| = |pts[2]-pts[1]| * 2**(-l)``.
'ndin'
A rank-1 integer array of length P+2. After the first integration
over the intervals (pts[1], pts[2]), the error estimates over some
of the intervals may have been increased artificially in order to
put their subdivision forward. This array has ones in slots
corresponding to the subintervals for which this happens.
**Weighting the integrand**
The input variables, *weight* and *wvar*, are used to weight the
integrand by a select list of functions. Different integration
methods are used to compute the integral with these weighting
functions, and these do not support specifying break points. The
possible values of weight and the corresponding weighting functions are.
========== =================================== =====================
``weight`` Weight function used ``wvar``
========== =================================== =====================
'cos' cos(w*x) wvar = w
'sin' sin(w*x) wvar = w
'alg' g(x) = ((x-a)**alpha)*((b-x)**beta) wvar = (alpha, beta)
'alg-loga' g(x)*log(x-a) wvar = (alpha, beta)
'alg-logb' g(x)*log(b-x) wvar = (alpha, beta)
'alg-log' g(x)*log(x-a)*log(b-x) wvar = (alpha, beta)
'cauchy' 1/(x-c) wvar = c
========== =================================== =====================
wvar holds the parameter w, (alpha, beta), or c depending on the weight
selected. In these expressions, a and b are the integration limits.
For the 'cos' and 'sin' weighting, additional inputs and outputs are
available.
For finite integration limits, the integration is performed using a
Clenshaw-Curtis method which uses Chebyshev moments. For repeated
calculations, these moments are saved in the output dictionary:
'momcom'
The maximum level of Chebyshev moments that have been computed,
i.e., if ``M_c`` is ``infodict['momcom']`` then the moments have been
computed for intervals of length ``|b-a| * 2**(-l)``,
``l=0,1,...,M_c``.
'nnlog'
A rank-1 integer array of length M(=limit), containing the
subdivision levels of the subintervals, i.e., an element of this
array is equal to l if the corresponding subinterval is
``|b-a|* 2**(-l)``.
'chebmo'
A rank-2 array of shape (25, maxp1) containing the computed
Chebyshev moments. These can be passed on to an integration
over the same interval by passing this array as the second
element of the sequence wopts and passing infodict['momcom'] as
the first element.
If one of the integration limits is infinite, then a Fourier integral is
computed (assuming w neq 0). If full_output is 1 and a numerical error
is encountered, besides the error message attached to the output tuple,
a dictionary is also appended to the output tuple which translates the
error codes in the array ``info['ierlst']`` to English messages. The
output information dictionary contains the following entries instead of
'last', 'alist', 'blist', 'rlist', and 'elist':
'lst'
The number of subintervals needed for the integration (call it ``K_f``).
'rslst'
A rank-1 array of length M_f=limlst, whose first ``K_f`` elements
contain the integral contribution over the interval
``(a+(k-1)c, a+kc)`` where ``c = (2*floor(|w|) + 1) * pi / |w|``
and ``k=1,2,...,K_f``.
'erlst'
A rank-1 array of length ``M_f`` containing the error estimate
corresponding to the interval in the same position in
``infodict['rslist']``.
'ierlst'
A rank-1 integer array of length ``M_f`` containing an error flag
corresponding to the interval in the same position in
``infodict['rslist']``. See the explanation dictionary (last entry
in the output tuple) for the meaning of the codes.
Examples
--------
Calculate :math:`\\int^4_0 x^2 dx` and compare with an analytic result
>>> from scipy import integrate
>>> x2 = lambda x: x**2
>>> integrate.quad(x2, 0, 4)
(21.333333333333332, 2.3684757858670003e-13)
>>> print(4**3 / 3.) # analytical result
21.3333333333
Calculate :math:`\\int^\\infty_0 e^{-x} dx`
>>> invexp = lambda x: np.exp(-x)
>>> integrate.quad(invexp, 0, np.inf)
(1.0, 5.842605999138044e-11)
>>> f = lambda x,a : a*x
>>> y, err = integrate.quad(f, 0, 1, args=(1,))
>>> y
0.5
>>> y, err = integrate.quad(f, 0, 1, args=(3,))
>>> y
1.5
Calculate :math:`\\int^1_0 x^2 + y^2 dx` with ctypes, holding
y parameter as 1::
testlib.c =>
double func(int n, double args[n]){
return args[0]*args[0] + args[1]*args[1];}
compile to library testlib.*
::
from scipy import integrate
import ctypes
lib = ctypes.CDLL('/home/.../testlib.*') #use absolute path
lib.func.restype = ctypes.c_double
lib.func.argtypes = (ctypes.c_int,ctypes.c_double)
integrate.quad(lib.func,0,1,(1))
#(1.3333333333333333, 1.4802973661668752e-14)
print((1.0**3/3.0 + 1.0) - (0.0**3/3.0 + 0.0)) #Analytic result
# 1.3333333333333333
Be aware that pulse shapes and other sharp features as compared to the
size of the integration interval may not be integrated correctly using
this method. A simplified example of this limitation is integrating a
y-axis reflected step function with many zero values within the integrals
bounds.
>>> y = lambda x: 1 if x<=0 else 0
>>> integrate.quad(y, -1, 1)
(1.0, 1.1102230246251565e-14)
>>> integrate.quad(y, -1, 100)
(1.0000000002199108, 1.0189464580163188e-08)
>>> integrate.quad(y, -1, 10000)
(0.0, 0.0)
"""
if not isinstance(args, tuple):
args = (args,)
# check the limits of integration: \int_a^b, expect a < b
flip, a, b = b < a, min(a, b), max(a, b)
if weight is None:
retval = _quad(func, a, b, args, full_output, epsabs, epsrel, limit,
points)
else:
if points is not None:
msg = ("Break points cannot be specified when using weighted integrand.\n"
"Continuing, ignoring specified points.")
warnings.warn(msg, IntegrationWarning, stacklevel=2)
retval = _quad_weight(func, a, b, args, full_output, epsabs, epsrel,
limlst, limit, maxp1, weight, wvar, wopts)
if flip:
retval = (-retval[0],) + retval[1:]
ier = retval[-1]
if ier == 0:
return retval[:-1]
msgs = {80: "A Python error occurred possibly while calling the function.",
1: "The maximum number of subdivisions (%d) has been achieved.\n If increasing the limit yields no improvement it is advised to analyze \n the integrand in order to determine the difficulties. If the position of a \n local difficulty can be determined (singularity, discontinuity) one will \n probably gain from splitting up the interval and calling the integrator \n on the subranges. Perhaps a special-purpose integrator should be used." % limit,
2: "The occurrence of roundoff error is detected, which prevents \n the requested tolerance from being achieved. The error may be \n underestimated.",
3: "Extremely bad integrand behavior occurs at some points of the\n integration interval.",
4: "The algorithm does not converge. Roundoff error is detected\n in the extrapolation table. It is assumed that the requested tolerance\n cannot be achieved, and that the returned result (if full_output = 1) is \n the best which can be obtained.",
5: "The integral is probably divergent, or slowly convergent.",
6: "The input is invalid.",
7: "Abnormal termination of the routine. The estimates for result\n and error are less reliable. It is assumed that the requested accuracy\n has not been achieved.",
'unknown': "Unknown error."}
if weight in ['cos','sin'] and (b == Inf or a == -Inf):
msgs[1] = "The maximum number of cycles allowed has been achieved., e.e.\n of subintervals (a+(k-1)c, a+kc) where c = (2*int(abs(omega)+1))\n *pi/abs(omega), for k = 1, 2, ..., lst. One can allow more cycles by increasing the value of limlst. Look at info['ierlst'] with full_output=1."
msgs[4] = "The extrapolation table constructed for convergence acceleration\n of the series formed by the integral contributions over the cycles, \n does not converge to within the requested accuracy. Look at \n info['ierlst'] with full_output=1."
msgs[7] = "Bad integrand behavior occurs within one or more of the cycles.\n Location and type of the difficulty involved can be determined from \n the vector info['ierlist'] obtained with full_output=1."
explain = {1: "The maximum number of subdivisions (= limit) has been \n achieved on this cycle.",
2: "The occurrence of roundoff error is detected and prevents\n the tolerance imposed on this cycle from being achieved.",
3: "Extremely bad integrand behavior occurs at some points of\n this cycle.",
4: "The integral over this cycle does not converge (to within the required accuracy) due to roundoff in the extrapolation procedure invoked on this cycle. It is assumed that the result on this interval is the best which can be obtained.",
5: "The integral over this cycle is probably divergent or slowly convergent."}
try:
msg = msgs[ier]
except KeyError:
msg = msgs['unknown']
if ier in [1,2,3,4,5,7]:
if full_output:
if weight in ['cos', 'sin'] and (b == Inf or a == -Inf):
return retval[:-1] + (msg, explain)
else:
return retval[:-1] + (msg,)
else:
warnings.warn(msg, IntegrationWarning, stacklevel=2)
return retval[:-1]
elif ier == 6: # Forensic decision tree when QUADPACK throws ier=6
if epsabs <= 0: # Small error tolerance - applies to all methods
if epsrel < max(50 * sys.float_info.epsilon, 5e-29):
msg = ("If 'epsabs'<=0, 'epsrel' must be greater than both"
" 5e-29 and 50*(machine epsilon).")
elif weight in ['sin', 'cos'] and (abs(a) + abs(b) == Inf):
msg = ("Sine or cosine weighted intergals with infinite domain"
" must have 'epsabs'>0.")
elif weight is None:
if points is None: # QAGSE/QAGIE
msg = ("Invalid 'limit' argument. There must be"
" at least one subinterval")
else: # QAGPE
if not (min(a, b) <= min(points) <= max(points) <= max(a, b)):
msg = ("All break points in 'points' must lie within the"
" integration limits.")
elif len(points) >= limit:
msg = ("Number of break points ({:d})"
" must be less than subinterval"
" limit ({:d})").format(len(points), limit)
else:
if maxp1 < 1:
msg = "Chebyshev moment limit maxp1 must be >=1."
elif weight in ('cos', 'sin') and abs(a+b) == Inf: # QAWFE
msg = "Cycle limit limlst must be >=3."
elif weight.startswith('alg'): # QAWSE
if min(wvar) < -1:
msg = "wvar parameters (alpha, beta) must both be >= -1."
if b < a:
msg = "Integration limits a, b must satistfy a<b."
elif weight == 'cauchy' and wvar in (a, b):
msg = ("Parameter 'wvar' must not equal"
" integration limits 'a' or 'b'.")
raise ValueError(msg)
def _quad(func,a,b,args,full_output,epsabs,epsrel,limit,points):
infbounds = 0
if (b != Inf and a != -Inf):
pass # standard integration
elif (b == Inf and a != -Inf):
infbounds = 1
bound = a
elif (b == Inf and a == -Inf):
infbounds = 2
bound = 0 # ignored
elif (b != Inf and a == -Inf):
infbounds = -1
bound = b
else:
raise RuntimeError("Infinity comparisons don't work for you.")
if points is None:
if infbounds == 0:
return _quadpack._qagse(func,a,b,args,full_output,epsabs,epsrel,limit)
else:
return _quadpack._qagie(func,bound,infbounds,args,full_output,epsabs,epsrel,limit)
else:
if infbounds != 0:
raise ValueError("Infinity inputs cannot be used with break points.")
else:
#Duplicates force function evaluation at singular points
the_points = numpy.unique(points)
the_points = the_points[a < the_points]
the_points = the_points[the_points < b]
the_points = numpy.concatenate((the_points, (0., 0.)))
return _quadpack._qagpe(func,a,b,the_points,args,full_output,epsabs,epsrel,limit)
def _quad_weight(func,a,b,args,full_output,epsabs,epsrel,limlst,limit,maxp1,weight,wvar,wopts):
if weight not in ['cos','sin','alg','alg-loga','alg-logb','alg-log','cauchy']:
raise ValueError("%s not a recognized weighting function." % weight)
strdict = {'cos':1,'sin':2,'alg':1,'alg-loga':2,'alg-logb':3,'alg-log':4}
if weight in ['cos','sin']:
integr = strdict[weight]
if (b != Inf and a != -Inf): # finite limits
if wopts is None: # no precomputed Chebyshev moments
return _quadpack._qawoe(func, a, b, wvar, integr, args, full_output,
epsabs, epsrel, limit, maxp1,1)
else: # precomputed Chebyshev moments
momcom = wopts[0]
chebcom = wopts[1]
return _quadpack._qawoe(func, a, b, wvar, integr, args, full_output,
epsabs, epsrel, limit, maxp1, 2, momcom, chebcom)
elif (b == Inf and a != -Inf):
return _quadpack._qawfe(func, a, wvar, integr, args, full_output,
epsabs,limlst,limit,maxp1)
elif (b != Inf and a == -Inf): # remap function and interval
if weight == 'cos':
def thefunc(x,*myargs):
y = -x
func = myargs[0]
myargs = (y,) + myargs[1:]
return func(*myargs)
else:
def thefunc(x,*myargs):
y = -x
func = myargs[0]
myargs = (y,) + myargs[1:]
return -func(*myargs)
args = (func,) + args
return _quadpack._qawfe(thefunc, -b, wvar, integr, args,
full_output, epsabs, limlst, limit, maxp1)
else:
raise ValueError("Cannot integrate with this weight from -Inf to +Inf.")
else:
if a in [-Inf,Inf] or b in [-Inf,Inf]:
raise ValueError("Cannot integrate with this weight over an infinite interval.")
if weight.startswith('alg'):
integr = strdict[weight]
return _quadpack._qawse(func, a, b, wvar, integr, args,
full_output, epsabs, epsrel, limit)
else: # weight == 'cauchy'
return _quadpack._qawce(func, a, b, wvar, args, full_output,
epsabs, epsrel, limit)
def dblquad(func, a, b, gfun, hfun, args=(), epsabs=1.49e-8, epsrel=1.49e-8):
"""
Compute a double integral.
Return the double (definite) integral of ``func(y, x)`` from ``x = a..b``
and ``y = gfun(x)..hfun(x)``.
Parameters
----------
func : callable
A Python function or method of at least two variables: y must be the
first argument and x the second argument.
a, b : float
The limits of integration in x: `a` < `b`
gfun : callable or float
The lower boundary curve in y which is a function taking a single
floating point argument (x) and returning a floating point result
or a float indicating a constant boundary curve.
hfun : callable or float
The upper boundary curve in y (same requirements as `gfun`).
args : sequence, optional
Extra arguments to pass to `func`.
epsabs : float, optional
Absolute tolerance passed directly to the inner 1-D quadrature
integration. Default is 1.49e-8. `dblquad`` tries to obtain
an accuracy of ``abs(i-result) <= max(epsabs, epsrel*abs(i))``
where ``i`` = inner integral of ``func(y, x)`` from ``gfun(x)``
to ``hfun(x)``, and ``result`` is the numerical approximation.
See `epsrel` below.
epsrel : float, optional
Relative tolerance of the inner 1-D integrals. Default is 1.49e-8.
If ``epsabs <= 0``, `epsrel` must be greater than both 5e-29
and ``50 * (machine epsilon)``. See `epsabs` above.
Returns
-------
y : float
The resultant integral.
abserr : float
An estimate of the error.
See also
--------
quad : single integral
tplquad : triple integral
nquad : N-dimensional integrals
fixed_quad : fixed-order Gaussian quadrature
quadrature : adaptive Gaussian quadrature
odeint : ODE integrator
ode : ODE integrator
simps : integrator for sampled data
romb : integrator for sampled data
scipy.special : for coefficients and roots of orthogonal polynomials
Examples
--------
Compute the double integral of ``x * y**2`` over the box
``x`` ranging from 0 to 2 and ``y`` ranging from 0 to 1.
>>> from scipy import integrate
>>> f = lambda y, x: x*y**2
>>> integrate.dblquad(f, 0, 2, lambda x: 0, lambda x: 1)
(0.6666666666666667, 7.401486830834377e-15)
"""
def temp_ranges(*args):
return [gfun(args[0]) if callable(gfun) else gfun,
hfun(args[0]) if callable(hfun) else hfun]
return nquad(func, [temp_ranges, [a, b]], args=args,
opts={"epsabs": epsabs, "epsrel": epsrel})
def tplquad(func, a, b, gfun, hfun, qfun, rfun, args=(), epsabs=1.49e-8,
epsrel=1.49e-8):
"""
Compute a triple (definite) integral.
Return the triple integral of ``func(z, y, x)`` from ``x = a..b``,
``y = gfun(x)..hfun(x)``, and ``z = qfun(x,y)..rfun(x,y)``.
Parameters
----------
func : function
A Python function or method of at least three variables in the
order (z, y, x).
a, b : float
The limits of integration in x: `a` < `b`
gfun : function or float
The lower boundary curve in y which is a function taking a single
floating point argument (x) and returning a floating point result
or a float indicating a constant boundary curve.
hfun : function or float
The upper boundary curve in y (same requirements as `gfun`).
qfun : function or float
The lower boundary surface in z. It must be a function that takes
two floats in the order (x, y) and returns a float or a float
indicating a constant boundary surface.
rfun : function or float
The upper boundary surface in z. (Same requirements as `qfun`.)
args : tuple, optional
Extra arguments to pass to `func`.
epsabs : float, optional
Absolute tolerance passed directly to the innermost 1-D quadrature
integration. Default is 1.49e-8.
epsrel : float, optional
Relative tolerance of the innermost 1-D integrals. Default is 1.49e-8.
Returns
-------
y : float
The resultant integral.
abserr : float
An estimate of the error.
See Also
--------
quad: Adaptive quadrature using QUADPACK
quadrature: Adaptive Gaussian quadrature
fixed_quad: Fixed-order Gaussian quadrature
dblquad: Double integrals
nquad : N-dimensional integrals
romb: Integrators for sampled data
simps: Integrators for sampled data
ode: ODE integrators
odeint: ODE integrators
scipy.special: For coefficients and roots of orthogonal polynomials
Examples
--------
Compute the triple integral of ``x * y * z``, over ``x`` ranging
from 1 to 2, ``y`` ranging from 2 to 3, ``z`` ranging from 0 to 1.
>>> from scipy import integrate
>>> f = lambda z, y, x: x*y*z
>>> integrate.tplquad(f, 1, 2, lambda x: 2, lambda x: 3,
... lambda x, y: 0, lambda x, y: 1)
(1.8750000000000002, 3.324644794257407e-14)
"""
# f(z, y, x)
# qfun/rfun (x, y)
# gfun/hfun(x)
# nquad will hand (y, x, t0, ...) to ranges0
# nquad will hand (x, t0, ...) to ranges1
# Stupid different API...
def ranges0(*args):
return [qfun(args[1], args[0]) if callable(qfun) else qfun,
rfun(args[1], args[0]) if callable(rfun) else rfun]
def ranges1(*args):
return [gfun(args[0]) if callable(gfun) else gfun,
hfun(args[0]) if callable(hfun) else hfun]
ranges = [ranges0, ranges1, [a, b]]
return nquad(func, ranges, args=args,
opts={"epsabs": epsabs, "epsrel": epsrel})
def nquad(func, ranges, args=None, opts=None, full_output=False):
"""
Integration over multiple variables.
Wraps `quad` to enable integration over multiple variables.
Various options allow improved integration of discontinuous functions, as
well as the use of weighted integration, and generally finer control of the
integration process.
Parameters
----------
func : {callable, scipy.LowLevelCallable}
The function to be integrated. Has arguments of ``x0, ... xn``,
``t0, tm``, where integration is carried out over ``x0, ... xn``, which
must be floats. Function signature should be
``func(x0, x1, ..., xn, t0, t1, ..., tm)``. Integration is carried out
in order. That is, integration over ``x0`` is the innermost integral,
and ``xn`` is the outermost.
If the user desires improved integration performance, then `f` may
be a `scipy.LowLevelCallable` with one of the signatures::
double func(int n, double *xx)
double func(int n, double *xx, void *user_data)
where ``n`` is the number of extra parameters and args is an array
of doubles of the additional parameters, the ``xx`` array contains the
coordinates. The ``user_data`` is the data contained in the
`scipy.LowLevelCallable`.
ranges : iterable object
Each element of ranges may be either a sequence of 2 numbers, or else
a callable that returns such a sequence. ``ranges[0]`` corresponds to
integration over x0, and so on. If an element of ranges is a callable,
then it will be called with all of the integration arguments available,
as well as any parametric arguments. e.g., if
``func = f(x0, x1, x2, t0, t1)``, then ``ranges[0]`` may be defined as
either ``(a, b)`` or else as ``(a, b) = range0(x1, x2, t0, t1)``.
args : iterable object, optional
Additional arguments ``t0, ..., tn``, required by `func`, `ranges`, and
``opts``.
opts : iterable object or dict, optional
Options to be passed to `quad`. May be empty, a dict, or
a sequence of dicts or functions that return a dict. If empty, the
default options from scipy.integrate.quad are used. If a dict, the same
options are used for all levels of integraion. If a sequence, then each
element of the sequence corresponds to a particular integration. e.g.,
opts[0] corresponds to integration over x0, and so on. If a callable,
the signature must be the same as for ``ranges``. The available
options together with their default values are:
- epsabs = 1.49e-08
- epsrel = 1.49e-08
- limit = 50
- points = None
- weight = None
- wvar = None
- wopts = None
For more information on these options, see `quad` and `quad_explain`.
full_output : bool, optional
Partial implementation of ``full_output`` from scipy.integrate.quad.
The number of integrand function evaluations ``neval`` can be obtained
by setting ``full_output=True`` when calling nquad.
Returns
-------
result : float
The result of the integration.
abserr : float
The maximum of the estimates of the absolute error in the various
integration results.
out_dict : dict, optional
A dict containing additional information on the integration.
See Also
--------
quad : 1-D numerical integration
dblquad, tplquad : double and triple integrals
fixed_quad : fixed-order Gaussian quadrature
quadrature : adaptive Gaussian quadrature
Examples
--------
>>> from scipy import integrate
>>> func = lambda x0,x1,x2,x3 : x0**2 + x1*x2 - x3**3 + np.sin(x0) + (
... 1 if (x0-.2*x3-.5-.25*x1>0) else 0)
>>> points = [[lambda x1,x2,x3 : 0.2*x3 + 0.5 + 0.25*x1], [], [], []]
>>> def opts0(*args, **kwargs):
... return {'points':[0.2*args[2] + 0.5 + 0.25*args[0]]}
>>> integrate.nquad(func, [[0,1], [-1,1], [.13,.8], [-.15,1]],
... opts=[opts0,{},{},{}], full_output=True)
(1.5267454070738633, 2.9437360001402324e-14, {'neval': 388962})
>>> scale = .1
>>> def func2(x0, x1, x2, x3, t0, t1):
... return x0*x1*x3**2 + np.sin(x2) + 1 + (1 if x0+t1*x1-t0>0 else 0)
>>> def lim0(x1, x2, x3, t0, t1):
... return [scale * (x1**2 + x2 + np.cos(x3)*t0*t1 + 1) - 1,
... scale * (x1**2 + x2 + np.cos(x3)*t0*t1 + 1) + 1]
>>> def lim1(x2, x3, t0, t1):
... return [scale * (t0*x2 + t1*x3) - 1,
... scale * (t0*x2 + t1*x3) + 1]
>>> def lim2(x3, t0, t1):
... return [scale * (x3 + t0**2*t1**3) - 1,
... scale * (x3 + t0**2*t1**3) + 1]
>>> def lim3(t0, t1):
... return [scale * (t0+t1) - 1, scale * (t0+t1) + 1]
>>> def opts0(x1, x2, x3, t0, t1):
... return {'points' : [t0 - t1*x1]}
>>> def opts1(x2, x3, t0, t1):
... return {}
>>> def opts2(x3, t0, t1):
... return {}
>>> def opts3(t0, t1):
... return {}
>>> integrate.nquad(func2, [lim0, lim1, lim2, lim3], args=(0,0),
... opts=[opts0, opts1, opts2, opts3])
(25.066666666666666, 2.7829590483937256e-13)
"""
depth = len(ranges)
ranges = [rng if callable(rng) else _RangeFunc(rng) for rng in ranges]
if args is None:
args = ()
if opts is None:
opts = [dict([])] * depth
if isinstance(opts, dict):
opts = [_OptFunc(opts)] * depth
else:
opts = [opt if callable(opt) else _OptFunc(opt) for opt in opts]
return _NQuad(func, ranges, opts, full_output).integrate(*args)
class _RangeFunc(object):
def __init__(self, range_):
self.range_ = range_
def __call__(self, *args):
"""Return stored value.
*args needed because range_ can be float or func, and is called with
variable number of parameters.
"""
return self.range_
class _OptFunc(object):
def __init__(self, opt):
self.opt = opt
def __call__(self, *args):
"""Return stored dict."""
return self.opt
class _NQuad(object):
def __init__(self, func, ranges, opts, full_output):
self.abserr = 0
self.func = func
self.ranges = ranges
self.opts = opts
self.maxdepth = len(ranges)
self.full_output = full_output
if self.full_output:
self.out_dict = {'neval': 0}
def integrate(self, *args, **kwargs):
depth = kwargs.pop('depth', 0)
if kwargs:
raise ValueError('unexpected kwargs')
# Get the integration range and options for this depth.
ind = -(depth + 1)
fn_range = self.ranges[ind]
low, high = fn_range(*args)
fn_opt = self.opts[ind]
opt = dict(fn_opt(*args))
if 'points' in opt:
opt['points'] = [x for x in opt['points'] if low <= x <= high]
if depth + 1 == self.maxdepth:
f = self.func
else:
f = partial(self.integrate, depth=depth+1)
quad_r = quad(f, low, high, args=args, full_output=self.full_output,
**opt)
value = quad_r[0]
abserr = quad_r[1]
if self.full_output:
infodict = quad_r[2]
# The 'neval' parameter in full_output returns the total
# number of times the integrand function was evaluated.
# Therefore, only the innermost integration loop counts.
if depth + 1 == self.maxdepth:
self.out_dict['neval'] += infodict['neval']
self.abserr = max(self.abserr, abserr)
if depth > 0:
return value
else:
# Final result of N-D integration with error
if self.full_output:
return value, self.abserr, self.out_dict
else:
return value, self.abserr

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@ -0,0 +1,113 @@
import os
from os.path import join
from scipy._build_utils import numpy_nodepr_api
def configuration(parent_package='',top_path=None):
from numpy.distutils.misc_util import Configuration
from scipy._build_utils.system_info import get_info
from scipy._build_utils import (uses_blas64, blas_ilp64_pre_build_hook,
combine_dict, get_f2py_int64_options)
config = Configuration('integrate', parent_package, top_path)
if uses_blas64():
lapack_opt = get_info('lapack_ilp64_opt', 2)
pre_build_hook = blas_ilp64_pre_build_hook(lapack_opt)
f2py_options = get_f2py_int64_options()
else:
lapack_opt = get_info('lapack_opt')
pre_build_hook = None
f2py_options = None
mach_src = [join('mach','*.f')]
quadpack_src = [join('quadpack', '*.f')]
lsoda_src = [join('odepack', fn) for fn in [
'blkdta000.f', 'bnorm.f', 'cfode.f',
'ewset.f', 'fnorm.f', 'intdy.f',
'lsoda.f', 'prja.f', 'solsy.f', 'srcma.f',
'stoda.f', 'vmnorm.f', 'xerrwv.f', 'xsetf.f',
'xsetun.f']]
vode_src = [join('odepack', 'vode.f'), join('odepack', 'zvode.f')]
dop_src = [join('dop','*.f')]
quadpack_test_src = [join('tests','_test_multivariate.c')]
odeint_banded_test_src = [join('tests', 'banded5x5.f')]
config.add_library('mach', sources=mach_src, config_fc={'noopt': (__file__, 1)},
_pre_build_hook=pre_build_hook)
config.add_library('quadpack', sources=quadpack_src, _pre_build_hook=pre_build_hook)
config.add_library('lsoda', sources=lsoda_src, _pre_build_hook=pre_build_hook)
config.add_library('vode', sources=vode_src, _pre_build_hook=pre_build_hook)
config.add_library('dop', sources=dop_src, _pre_build_hook=pre_build_hook)
# Extensions
# quadpack:
include_dirs = [join(os.path.dirname(__file__), '..', '_lib', 'src')]
cfg = combine_dict(lapack_opt,
include_dirs=include_dirs,
libraries=['quadpack', 'mach'])
config.add_extension('_quadpack',
sources=['_quadpackmodule.c'],
depends=(['__quadpack.h']
+ quadpack_src + mach_src),
**cfg)
# odepack/lsoda-odeint
cfg = combine_dict(lapack_opt, numpy_nodepr_api,
libraries=['lsoda', 'mach'])
config.add_extension('_odepack',
sources=['_odepackmodule.c'],
depends=(lsoda_src + mach_src),
**cfg)
# vode
cfg = combine_dict(lapack_opt,
libraries=['vode'])
ext = config.add_extension('vode',
sources=['vode.pyf'],
depends=vode_src,
f2py_options=f2py_options,
**cfg)
ext._pre_build_hook = pre_build_hook
# lsoda
cfg = combine_dict(lapack_opt,
libraries=['lsoda', 'mach'])
ext = config.add_extension('lsoda',
sources=['lsoda.pyf'],
depends=(lsoda_src + mach_src),
f2py_options=f2py_options,
**cfg)
ext._pre_build_hook = pre_build_hook
# dop
ext = config.add_extension('_dop',
sources=['dop.pyf'],
libraries=['dop'],
depends=dop_src,
f2py_options=f2py_options)
ext._pre_build_hook = pre_build_hook
config.add_extension('_test_multivariate',
sources=quadpack_test_src)
# Fortran+f2py extension module for testing odeint.
cfg = combine_dict(lapack_opt,
libraries=['lsoda', 'mach'])
ext = config.add_extension('_test_odeint_banded',
sources=odeint_banded_test_src,
depends=(lsoda_src + mach_src),
f2py_options=f2py_options,
**cfg)
ext._pre_build_hook = pre_build_hook
config.add_subpackage('_ivp')
config.add_data_dir('tests')
return config
if __name__ == '__main__':
from numpy.distutils.core import setup
setup(**configuration(top_path='').todict())

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#include <Python.h>
#include "math.h"
const double PI = 3.141592653589793238462643383279502884;
static double
_multivariate_typical(int n, double *args)
{
return cos(args[1] * args[0] - args[2] * sin(args[0])) / PI;
}
static double
_multivariate_indefinite(int n, double *args)
{
return -exp(-args[0]) * log(args[0]);
}
static double
_multivariate_sin(int n, double *args)
{
return sin(args[0]);
}
static double
_sin_0(double x, void *user_data)
{
return sin(x);
}
static double
_sin_1(int ndim, double *x, void *user_data)
{
return sin(x[0]);
}
static double
_sin_2(double x)
{
return sin(x);
}
static double
_sin_3(int ndim, double *x)
{
return sin(x[0]);
}
typedef struct {
char *name;
void *ptr;
} routine_t;
static const routine_t routines[] = {
{"_multivariate_typical", &_multivariate_typical},
{"_multivariate_indefinite", &_multivariate_indefinite},
{"_multivariate_sin", &_multivariate_sin},
{"_sin_0", &_sin_0},
{"_sin_1", &_sin_1},
{"_sin_2", &_sin_2},
{"_sin_3", &_sin_3}
};
static int create_pointers(PyObject *module)
{
PyObject *d, *obj = NULL;
int i;
d = PyModule_GetDict(module);
if (d == NULL) {
goto fail;
}
for (i = 0; i < sizeof(routines) / sizeof(routine_t); ++i) {
obj = PyLong_FromVoidPtr(routines[i].ptr);
if (obj == NULL) {
goto fail;
}
if (PyDict_SetItemString(d, routines[i].name, obj)) {
goto fail;
}
Py_DECREF(obj);
obj = NULL;
}
Py_XDECREF(obj);
return 0;
fail:
Py_XDECREF(obj);
return -1;
}
static struct PyModuleDef moduledef = {
PyModuleDef_HEAD_INIT,
"_test_multivariate",
NULL,
-1,
NULL, /* Empty methods section */
NULL,
NULL,
NULL,
NULL
};
PyMODINIT_FUNC
PyInit__test_multivariate(void)
{
PyObject *m;
m = PyModule_Create(&moduledef);
if (m == NULL) {
return NULL;
}
if (create_pointers(m)) {
Py_DECREF(m);
return NULL;
}
return m;
}

View file

@ -0,0 +1,240 @@
c banded5x5.f
c
c This Fortran library contains implementations of the
c differential equation
c dy/dt = A*y
c where A is a 5x5 banded matrix (see below for the actual
c values). These functions will be used to test
c scipy.integrate.odeint.
c
c The idea is to solve the system two ways: pure Fortran, and
c using odeint. The "pure Fortran" solver is implemented in
c the subroutine banded5x5_solve below. It calls LSODA to
c solve the system.
c
c To solve the same system using odeint, the functions in this
c file are given a python wrapper using f2py. Then the code
c in test_odeint_jac.py uses the wrapper to implement the
c equation and Jacobian functions required by odeint. Because
c those functions ultimately call the Fortran routines defined
c in this file, the two method (pure Fortran and odeint) should
c produce exactly the same results. (That's assuming floating
c point calculations are deterministic, which can be an
c incorrect assumption.) If we simply re-implemented the
c equation and Jacobian functions using just python and numpy,
c the floating point calculations would not be performed in
c the same sequence as in the Fortran code, and we would obtain
c different answers. The answer for either method would be
c numerically "correct", but the errors would be different,
c and the counts of function and Jacobian evaluations would
c likely be different.
c
block data jacobian
implicit none
double precision bands
dimension bands(4,5)
common /jac/ bands
c The data for a banded Jacobian stored in packed banded
c format. The full Jacobian is
c
c -1, 0.25, 0, 0, 0
c 0.25, -5, 0.25, 0, 0
c 0.10, 0.25, -25, 0.25, 0
c 0, 0.10, 0.25, -125, 0.25
c 0, 0, 0.10, 0.25, -625
c
c The columns in the following layout of numbers are
c the upper diagonal, main diagonal and two lower diagonals
c (i.e. each row in the layout is a column of the packed
c banded Jacobian). The values 0.00D0 are in the "don't
c care" positions.
data bands/
+ 0.00D0, -1.0D0, 0.25D0, 0.10D0,
+ 0.25D0, -5.0D0, 0.25D0, 0.10D0,
+ 0.25D0, -25.0D0, 0.25D0, 0.10D0,
+ 0.25D0, -125.0D0, 0.25D0, 0.00D0,
+ 0.25D0, -625.0D0, 0.00D0, 0.00D0
+ /
end
subroutine getbands(jac)
double precision jac
dimension jac(4, 5)
cf2py intent(out) jac
double precision bands
dimension bands(4,5)
common /jac/ bands
integer i, j
do 5 i = 1, 4
do 5 j = 1, 5
jac(i, j) = bands(i, j)
5 continue
return
end
c
c Differential equations, right-hand-side
c
subroutine banded5x5(n, t, y, f)
implicit none
integer n
double precision t, y, f
dimension y(n), f(n)
double precision bands
dimension bands(4,5)
common /jac/ bands
f(1) = bands(2,1)*y(1) + bands(1,2)*y(2)
f(2) = bands(3,1)*y(1) + bands(2,2)*y(2) + bands(1,3)*y(3)
f(3) = bands(4,1)*y(1) + bands(3,2)*y(2) + bands(2,3)*y(3)
+ + bands(1,4)*y(4)
f(4) = bands(4,2)*y(2) + bands(3,3)*y(3) + bands(2,4)*y(4)
+ + bands(1,5)*y(5)
f(5) = bands(4,3)*y(3) + bands(3,4)*y(4) + bands(2,5)*y(5)
return
end
c
c Jacobian
c
c The subroutine assumes that the full Jacobian is to be computed.
c ml and mu are ignored, and nrowpd is assumed to be n.
c
subroutine banded5x5_jac(n, t, y, ml, mu, jac, nrowpd)
implicit none
integer n, ml, mu, nrowpd
double precision t, y, jac
dimension y(n), jac(nrowpd, n)
integer i, j
double precision bands
dimension bands(4,5)
common /jac/ bands
do 15 i = 1, 4
do 15 j = 1, 5
if ((i - j) .gt. 0) then
jac(i - j, j) = bands(i, j)
end if
15 continue
return
end
c
c Banded Jacobian
c
c ml = 2, mu = 1
c
subroutine banded5x5_bjac(n, t, y, ml, mu, bjac, nrowpd)
implicit none
integer n, ml, mu, nrowpd
double precision t, y, bjac
dimension y(5), bjac(nrowpd, n)
integer i, j
double precision bands
dimension bands(4,5)
common /jac/ bands
do 20 i = 1, 4
do 20 j = 1, 5
bjac(i, j) = bands(i, j)
20 continue
return
end
subroutine banded5x5_solve(y, nsteps, dt, jt, nst, nfe, nje)
c jt is the Jacobian type:
c jt = 1 Use the full Jacobian.
c jt = 4 Use the banded Jacobian.
c nst, nfe and nje are outputs:
c nst: Total number of internal steps
c nfe: Total number of function (i.e. right-hand-side)
c evaluations
c nje: Total number of Jacobian evaluations
implicit none
external banded5x5
external banded5x5_jac
external banded5x5_bjac
external LSODA
c Arguments...
double precision y, dt
integer nsteps, jt, nst, nfe, nje
cf2py intent(inout) y
cf2py intent(in) nsteps, dt, jt
cf2py intent(out) nst, nfe, nje
c Local variables...
double precision atol, rtol, t, tout, rwork
integer iwork
dimension y(5), rwork(500), iwork(500)
integer neq, i
integer itol, iopt, itask, istate, lrw, liw
c Common block...
double precision jacband
dimension jacband(4,5)
common /jac/ jacband
c --- t range ---
t = 0.0D0
c --- Solver tolerances ---
rtol = 1.0D-11
atol = 1.0D-13
itol = 1
c --- Other LSODA parameters ---
neq = 5
itask = 1
istate = 1
iopt = 0
iwork(1) = 2
iwork(2) = 1
lrw = 500
liw = 500
c --- Call LSODA in a loop to compute the solution ---
do 40 i = 1, nsteps
tout = i*dt
if (jt .eq. 1) then
call LSODA(banded5x5, neq, y, t, tout,
& itol, rtol, atol, itask, istate, iopt,
& rwork, lrw, iwork, liw,
& banded5x5_jac, jt)
else
call LSODA(banded5x5, neq, y, t, tout,
& itol, rtol, atol, itask, istate, iopt,
& rwork, lrw, iwork, liw,
& banded5x5_bjac, jt)
end if
40 if (istate .lt. 0) goto 80
nst = iwork(11)
nfe = iwork(12)
nje = iwork(13)
return
80 write (6,89) istate
89 format(1X,"Error: istate=",I3)
return
end

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import pytest
import numpy as np
from numpy.testing import assert_allclose
from scipy.integrate import quad_vec
quadrature_params = pytest.mark.parametrize('quadrature',
[None, "gk15", "gk21", "trapz"])
@quadrature_params
def test_quad_vec_simple(quadrature):
n = np.arange(10)
f = lambda x: x**n
for epsabs in [0.1, 1e-3, 1e-6]:
if quadrature == 'trapz' and epsabs < 1e-4:
# slow: skip
continue
kwargs = dict(epsabs=epsabs, quadrature=quadrature)
exact = 2**(n+1)/(n + 1)
res, err = quad_vec(f, 0, 2, norm='max', **kwargs)
assert_allclose(res, exact, rtol=0, atol=epsabs)
res, err = quad_vec(f, 0, 2, norm='2', **kwargs)
assert np.linalg.norm(res - exact) < epsabs
res, err = quad_vec(f, 0, 2, norm='max', points=(0.5, 1.0), **kwargs)
assert_allclose(res, exact, rtol=0, atol=epsabs)
res, err, *rest = quad_vec(f, 0, 2, norm='max',
epsrel=1e-8,
full_output=True,
limit=10000,
**kwargs)
assert_allclose(res, exact, rtol=0, atol=epsabs)
@quadrature_params
def test_quad_vec_simple_inf(quadrature):
f = lambda x: 1 / (1 + np.float64(x)**2)
for epsabs in [0.1, 1e-3, 1e-6]:
if quadrature == 'trapz' and epsabs < 1e-4:
# slow: skip
continue
kwargs = dict(norm='max', epsabs=epsabs, quadrature=quadrature)
res, err = quad_vec(f, 0, np.inf, **kwargs)
assert_allclose(res, np.pi/2, rtol=0, atol=max(epsabs, err))
res, err = quad_vec(f, 0, -np.inf, **kwargs)
assert_allclose(res, -np.pi/2, rtol=0, atol=max(epsabs, err))
res, err = quad_vec(f, -np.inf, 0, **kwargs)
assert_allclose(res, np.pi/2, rtol=0, atol=max(epsabs, err))
res, err = quad_vec(f, np.inf, 0, **kwargs)
assert_allclose(res, -np.pi/2, rtol=0, atol=max(epsabs, err))
res, err = quad_vec(f, -np.inf, np.inf, **kwargs)
assert_allclose(res, np.pi, rtol=0, atol=max(epsabs, err))
res, err = quad_vec(f, np.inf, -np.inf, **kwargs)
assert_allclose(res, -np.pi, rtol=0, atol=max(epsabs, err))
res, err = quad_vec(f, np.inf, np.inf, **kwargs)
assert_allclose(res, 0, rtol=0, atol=max(epsabs, err))
res, err = quad_vec(f, -np.inf, -np.inf, **kwargs)
assert_allclose(res, 0, rtol=0, atol=max(epsabs, err))
res, err = quad_vec(f, 0, np.inf, points=(1.0, 2.0), **kwargs)
assert_allclose(res, np.pi/2, rtol=0, atol=max(epsabs, err))
f = lambda x: np.sin(x + 2) / (1 + x**2)
exact = np.pi / np.e * np.sin(2)
epsabs = 1e-5
res, err, info = quad_vec(f, -np.inf, np.inf, limit=1000, norm='max', epsabs=epsabs,
quadrature=quadrature, full_output=True)
assert info.status == 1
assert_allclose(res, exact, rtol=0, atol=max(epsabs, 1.5 * err))
def _lorenzian(x):
return 1 / (1 + x**2)
def test_quad_vec_pool():
from multiprocessing.dummy import Pool
f = _lorenzian
res, err = quad_vec(f, -np.inf, np.inf, norm='max', epsabs=1e-4, workers=4)
assert_allclose(res, np.pi, rtol=0, atol=1e-4)
with Pool(10) as pool:
f = lambda x: 1 / (1 + x**2)
res, err = quad_vec(f, -np.inf, np.inf, norm='max', epsabs=1e-4, workers=pool.map)
assert_allclose(res, np.pi, rtol=0, atol=1e-4)
@quadrature_params
def test_num_eval(quadrature):
def f(x):
count[0] += 1
return x**5
count = [0]
res = quad_vec(f, 0, 1, norm='max', full_output=True, quadrature=quadrature)
assert res[2].neval == count[0]
def test_info():
def f(x):
return np.ones((3, 2, 1))
res, err, info = quad_vec(f, 0, 1, norm='max', full_output=True)
assert info.success == True
assert info.status == 0
assert info.message == 'Target precision reached.'
assert info.neval > 0
assert info.intervals.shape[1] == 2
assert info.integrals.shape == (info.intervals.shape[0], 3, 2, 1)
assert info.errors.shape == (info.intervals.shape[0],)
def test_nan_inf():
def f_nan(x):
return np.nan
def f_inf(x):
return np.inf if x < 0.1 else 1/x
res, err, info = quad_vec(f_nan, 0, 1, full_output=True)
assert info.status == 3
res, err, info = quad_vec(f_inf, 0, 1, full_output=True)
assert info.status == 3
@pytest.mark.parametrize('a,b', [(0, 1), (0, np.inf), (np.inf, 0),
(-np.inf, np.inf), (np.inf, -np.inf)])
def test_points(a, b):
# Check that initial interval splitting is done according to
# `points`, by checking that consecutive sets of 15 point (for
# gk15) function evaluations lie between `points`
points = (0, 0.25, 0.5, 0.75, 1.0)
points += tuple(-x for x in points)
quadrature_points = 15
interval_sets = []
count = 0
def f(x):
nonlocal count
if count % quadrature_points == 0:
interval_sets.append(set())
count += 1
interval_sets[-1].add(float(x))
return 0.0
quad_vec(f, a, b, points=points, quadrature='gk15', limit=0)
# Check that all point sets lie in a single `points` interval
for p in interval_sets:
j = np.searchsorted(sorted(points), tuple(p))
assert np.all(j == j[0])

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@ -0,0 +1,218 @@
import itertools
import numpy as np
from numpy.testing import assert_allclose
from scipy.integrate import ode
def _band_count(a):
"""Returns ml and mu, the lower and upper band sizes of a."""
nrows, ncols = a.shape
ml = 0
for k in range(-nrows+1, 0):
if np.diag(a, k).any():
ml = -k
break
mu = 0
for k in range(nrows-1, 0, -1):
if np.diag(a, k).any():
mu = k
break
return ml, mu
def _linear_func(t, y, a):
"""Linear system dy/dt = a * y"""
return a.dot(y)
def _linear_jac(t, y, a):
"""Jacobian of a * y is a."""
return a
def _linear_banded_jac(t, y, a):
"""Banded Jacobian."""
ml, mu = _band_count(a)
bjac = [np.r_[[0] * k, np.diag(a, k)] for k in range(mu, 0, -1)]
bjac.append(np.diag(a))
for k in range(-1, -ml-1, -1):
bjac.append(np.r_[np.diag(a, k), [0] * (-k)])
return bjac
def _solve_linear_sys(a, y0, tend=1, dt=0.1,
solver=None, method='bdf', use_jac=True,
with_jacobian=False, banded=False):
"""Use scipy.integrate.ode to solve a linear system of ODEs.
a : square ndarray
Matrix of the linear system to be solved.
y0 : ndarray
Initial condition
tend : float
Stop time.
dt : float
Step size of the output.
solver : str
If not None, this must be "vode", "lsoda" or "zvode".
method : str
Either "bdf" or "adams".
use_jac : bool
Determines if the jacobian function is passed to ode().
with_jacobian : bool
Passed to ode.set_integrator().
banded : bool
Determines whether a banded or full jacobian is used.
If `banded` is True, `lband` and `uband` are determined by the
values in `a`.
"""
if banded:
lband, uband = _band_count(a)
else:
lband = None
uband = None
if use_jac:
if banded:
r = ode(_linear_func, _linear_banded_jac)
else:
r = ode(_linear_func, _linear_jac)
else:
r = ode(_linear_func)
if solver is None:
if np.iscomplexobj(a):
solver = "zvode"
else:
solver = "vode"
r.set_integrator(solver,
with_jacobian=with_jacobian,
method=method,
lband=lband, uband=uband,
rtol=1e-9, atol=1e-10,
)
t0 = 0
r.set_initial_value(y0, t0)
r.set_f_params(a)
r.set_jac_params(a)
t = [t0]
y = [y0]
while r.successful() and r.t < tend:
r.integrate(r.t + dt)
t.append(r.t)
y.append(r.y)
t = np.array(t)
y = np.array(y)
return t, y
def _analytical_solution(a, y0, t):
"""
Analytical solution to the linear differential equations dy/dt = a*y.
The solution is only valid if `a` is diagonalizable.
Returns a 2-D array with shape (len(t), len(y0)).
"""
lam, v = np.linalg.eig(a)
c = np.linalg.solve(v, y0)
e = c * np.exp(lam * t.reshape(-1, 1))
sol = e.dot(v.T)
return sol
def test_banded_ode_solvers():
# Test the "lsoda", "vode" and "zvode" solvers of the `ode` class
# with a system that has a banded Jacobian matrix.
t_exact = np.linspace(0, 1.0, 5)
# --- Real arrays for testing the "lsoda" and "vode" solvers ---
# lband = 2, uband = 1:
a_real = np.array([[-0.6, 0.1, 0.0, 0.0, 0.0],
[0.2, -0.5, 0.9, 0.0, 0.0],
[0.1, 0.1, -0.4, 0.1, 0.0],
[0.0, 0.3, -0.1, -0.9, -0.3],
[0.0, 0.0, 0.1, 0.1, -0.7]])
# lband = 0, uband = 1:
a_real_upper = np.triu(a_real)
# lband = 2, uband = 0:
a_real_lower = np.tril(a_real)
# lband = 0, uband = 0:
a_real_diag = np.triu(a_real_lower)
real_matrices = [a_real, a_real_upper, a_real_lower, a_real_diag]
real_solutions = []
for a in real_matrices:
y0 = np.arange(1, a.shape[0] + 1)
y_exact = _analytical_solution(a, y0, t_exact)
real_solutions.append((y0, t_exact, y_exact))
def check_real(idx, solver, meth, use_jac, with_jac, banded):
a = real_matrices[idx]
y0, t_exact, y_exact = real_solutions[idx]
t, y = _solve_linear_sys(a, y0,
tend=t_exact[-1],
dt=t_exact[1] - t_exact[0],
solver=solver,
method=meth,
use_jac=use_jac,
with_jacobian=with_jac,
banded=banded)
assert_allclose(t, t_exact)
assert_allclose(y, y_exact)
for idx in range(len(real_matrices)):
p = [['vode', 'lsoda'], # solver
['bdf', 'adams'], # method
[False, True], # use_jac
[False, True], # with_jacobian
[False, True]] # banded
for solver, meth, use_jac, with_jac, banded in itertools.product(*p):
check_real(idx, solver, meth, use_jac, with_jac, banded)
# --- Complex arrays for testing the "zvode" solver ---
# complex, lband = 2, uband = 1:
a_complex = a_real - 0.5j * a_real
# complex, lband = 0, uband = 0:
a_complex_diag = np.diag(np.diag(a_complex))
complex_matrices = [a_complex, a_complex_diag]
complex_solutions = []
for a in complex_matrices:
y0 = np.arange(1, a.shape[0] + 1) + 1j
y_exact = _analytical_solution(a, y0, t_exact)
complex_solutions.append((y0, t_exact, y_exact))
def check_complex(idx, solver, meth, use_jac, with_jac, banded):
a = complex_matrices[idx]
y0, t_exact, y_exact = complex_solutions[idx]
t, y = _solve_linear_sys(a, y0,
tend=t_exact[-1],
dt=t_exact[1] - t_exact[0],
solver=solver,
method=meth,
use_jac=use_jac,
with_jacobian=with_jac,
banded=banded)
assert_allclose(t, t_exact)
assert_allclose(y, y_exact)
for idx in range(len(complex_matrices)):
p = [['bdf', 'adams'], # method
[False, True], # use_jac
[False, True], # with_jacobian
[False, True]] # banded
for meth, use_jac, with_jac, banded in itertools.product(*p):
check_complex(idx, "zvode", meth, use_jac, with_jac, banded)

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@ -0,0 +1,602 @@
import sys
try:
from StringIO import StringIO
except ImportError:
from io import StringIO
import numpy as np
from numpy.testing import (assert_, assert_array_equal, assert_allclose,
assert_equal)
from pytest import raises as assert_raises
from scipy.sparse import coo_matrix
from scipy.special import erf
from scipy.integrate._bvp import (modify_mesh, estimate_fun_jac,
estimate_bc_jac, compute_jac_indices,
construct_global_jac, solve_bvp)
def exp_fun(x, y):
return np.vstack((y[1], y[0]))
def exp_fun_jac(x, y):
df_dy = np.empty((2, 2, x.shape[0]))
df_dy[0, 0] = 0
df_dy[0, 1] = 1
df_dy[1, 0] = 1
df_dy[1, 1] = 0
return df_dy
def exp_bc(ya, yb):
return np.hstack((ya[0] - 1, yb[0]))
def exp_bc_complex(ya, yb):
return np.hstack((ya[0] - 1 - 1j, yb[0]))
def exp_bc_jac(ya, yb):
dbc_dya = np.array([
[1, 0],
[0, 0]
])
dbc_dyb = np.array([
[0, 0],
[1, 0]
])
return dbc_dya, dbc_dyb
def exp_sol(x):
return (np.exp(-x) - np.exp(x - 2)) / (1 - np.exp(-2))
def sl_fun(x, y, p):
return np.vstack((y[1], -p[0]**2 * y[0]))
def sl_fun_jac(x, y, p):
n, m = y.shape
df_dy = np.empty((n, 2, m))
df_dy[0, 0] = 0
df_dy[0, 1] = 1
df_dy[1, 0] = -p[0]**2
df_dy[1, 1] = 0
df_dp = np.empty((n, 1, m))
df_dp[0, 0] = 0
df_dp[1, 0] = -2 * p[0] * y[0]
return df_dy, df_dp
def sl_bc(ya, yb, p):
return np.hstack((ya[0], yb[0], ya[1] - p[0]))
def sl_bc_jac(ya, yb, p):
dbc_dya = np.zeros((3, 2))
dbc_dya[0, 0] = 1
dbc_dya[2, 1] = 1
dbc_dyb = np.zeros((3, 2))
dbc_dyb[1, 0] = 1
dbc_dp = np.zeros((3, 1))
dbc_dp[2, 0] = -1
return dbc_dya, dbc_dyb, dbc_dp
def sl_sol(x, p):
return np.sin(p[0] * x)
def emden_fun(x, y):
return np.vstack((y[1], -y[0]**5))
def emden_fun_jac(x, y):
df_dy = np.empty((2, 2, x.shape[0]))
df_dy[0, 0] = 0
df_dy[0, 1] = 1
df_dy[1, 0] = -5 * y[0]**4
df_dy[1, 1] = 0
return df_dy
def emden_bc(ya, yb):
return np.array([ya[1], yb[0] - (3/4)**0.5])
def emden_bc_jac(ya, yb):
dbc_dya = np.array([
[0, 1],
[0, 0]
])
dbc_dyb = np.array([
[0, 0],
[1, 0]
])
return dbc_dya, dbc_dyb
def emden_sol(x):
return (1 + x**2/3)**-0.5
def undefined_fun(x, y):
return np.zeros_like(y)
def undefined_bc(ya, yb):
return np.array([ya[0], yb[0] - 1])
def big_fun(x, y):
f = np.zeros_like(y)
f[::2] = y[1::2]
return f
def big_bc(ya, yb):
return np.hstack((ya[::2], yb[::2] - 1))
def big_sol(x, n):
y = np.ones((2 * n, x.size))
y[::2] = x
return x
def shock_fun(x, y):
eps = 1e-3
return np.vstack((
y[1],
-(x * y[1] + eps * np.pi**2 * np.cos(np.pi * x) +
np.pi * x * np.sin(np.pi * x)) / eps
))
def shock_bc(ya, yb):
return np.array([ya[0] + 2, yb[0]])
def shock_sol(x):
eps = 1e-3
k = np.sqrt(2 * eps)
return np.cos(np.pi * x) + erf(x / k) / erf(1 / k)
def nonlin_bc_fun(x, y):
# laplace eq.
return np.stack([y[1], np.zeros_like(x)])
def nonlin_bc_bc(ya, yb):
phiA, phipA = ya
phiC, phipC = yb
kappa, ioA, ioC, V, f = 1.64, 0.01, 1.0e-4, 0.5, 38.9
# Butler-Volmer Kinetics at Anode
hA = 0.0-phiA-0.0
iA = ioA * (np.exp(f*hA) - np.exp(-f*hA))
res0 = iA + kappa * phipA
# Butler-Volmer Kinetics at Cathode
hC = V - phiC - 1.0
iC = ioC * (np.exp(f*hC) - np.exp(-f*hC))
res1 = iC - kappa*phipC
return np.array([res0, res1])
def nonlin_bc_sol(x):
return -0.13426436116763119 - 1.1308709 * x
def test_modify_mesh():
x = np.array([0, 1, 3, 9], dtype=float)
x_new = modify_mesh(x, np.array([0]), np.array([2]))
assert_array_equal(x_new, np.array([0, 0.5, 1, 3, 5, 7, 9]))
x = np.array([-6, -3, 0, 3, 6], dtype=float)
x_new = modify_mesh(x, np.array([1], dtype=int), np.array([0, 2, 3]))
assert_array_equal(x_new, [-6, -5, -4, -3, -1.5, 0, 1, 2, 3, 4, 5, 6])
def test_compute_fun_jac():
x = np.linspace(0, 1, 5)
y = np.empty((2, x.shape[0]))
y[0] = 0.01
y[1] = 0.02
p = np.array([])
df_dy, df_dp = estimate_fun_jac(lambda x, y, p: exp_fun(x, y), x, y, p)
df_dy_an = exp_fun_jac(x, y)
assert_allclose(df_dy, df_dy_an)
assert_(df_dp is None)
x = np.linspace(0, np.pi, 5)
y = np.empty((2, x.shape[0]))
y[0] = np.sin(x)
y[1] = np.cos(x)
p = np.array([1.0])
df_dy, df_dp = estimate_fun_jac(sl_fun, x, y, p)
df_dy_an, df_dp_an = sl_fun_jac(x, y, p)
assert_allclose(df_dy, df_dy_an)
assert_allclose(df_dp, df_dp_an)
x = np.linspace(0, 1, 10)
y = np.empty((2, x.shape[0]))
y[0] = (3/4)**0.5
y[1] = 1e-4
p = np.array([])
df_dy, df_dp = estimate_fun_jac(lambda x, y, p: emden_fun(x, y), x, y, p)
df_dy_an = emden_fun_jac(x, y)
assert_allclose(df_dy, df_dy_an)
assert_(df_dp is None)
def test_compute_bc_jac():
ya = np.array([-1.0, 2])
yb = np.array([0.5, 3])
p = np.array([])
dbc_dya, dbc_dyb, dbc_dp = estimate_bc_jac(
lambda ya, yb, p: exp_bc(ya, yb), ya, yb, p)
dbc_dya_an, dbc_dyb_an = exp_bc_jac(ya, yb)
assert_allclose(dbc_dya, dbc_dya_an)
assert_allclose(dbc_dyb, dbc_dyb_an)
assert_(dbc_dp is None)
ya = np.array([0.0, 1])
yb = np.array([0.0, -1])
p = np.array([0.5])
dbc_dya, dbc_dyb, dbc_dp = estimate_bc_jac(sl_bc, ya, yb, p)
dbc_dya_an, dbc_dyb_an, dbc_dp_an = sl_bc_jac(ya, yb, p)
assert_allclose(dbc_dya, dbc_dya_an)
assert_allclose(dbc_dyb, dbc_dyb_an)
assert_allclose(dbc_dp, dbc_dp_an)
ya = np.array([0.5, 100])
yb = np.array([-1000, 10.5])
p = np.array([])
dbc_dya, dbc_dyb, dbc_dp = estimate_bc_jac(
lambda ya, yb, p: emden_bc(ya, yb), ya, yb, p)
dbc_dya_an, dbc_dyb_an = emden_bc_jac(ya, yb)
assert_allclose(dbc_dya, dbc_dya_an)
assert_allclose(dbc_dyb, dbc_dyb_an)
assert_(dbc_dp is None)
def test_compute_jac_indices():
n = 2
m = 4
k = 2
i, j = compute_jac_indices(n, m, k)
s = coo_matrix((np.ones_like(i), (i, j))).toarray()
s_true = np.array([
[1, 1, 1, 1, 0, 0, 0, 0, 1, 1],
[1, 1, 1, 1, 0, 0, 0, 0, 1, 1],
[0, 0, 1, 1, 1, 1, 0, 0, 1, 1],
[0, 0, 1, 1, 1, 1, 0, 0, 1, 1],
[0, 0, 0, 0, 1, 1, 1, 1, 1, 1],
[0, 0, 0, 0, 1, 1, 1, 1, 1, 1],
[1, 1, 0, 0, 0, 0, 1, 1, 1, 1],
[1, 1, 0, 0, 0, 0, 1, 1, 1, 1],
[1, 1, 0, 0, 0, 0, 1, 1, 1, 1],
[1, 1, 0, 0, 0, 0, 1, 1, 1, 1],
])
assert_array_equal(s, s_true)
def test_compute_global_jac():
n = 2
m = 5
k = 1
i_jac, j_jac = compute_jac_indices(2, 5, 1)
x = np.linspace(0, 1, 5)
h = np.diff(x)
y = np.vstack((np.sin(np.pi * x), np.pi * np.cos(np.pi * x)))
p = np.array([3.0])
f = sl_fun(x, y, p)
x_middle = x[:-1] + 0.5 * h
y_middle = 0.5 * (y[:, :-1] + y[:, 1:]) - h/8 * (f[:, 1:] - f[:, :-1])
df_dy, df_dp = sl_fun_jac(x, y, p)
df_dy_middle, df_dp_middle = sl_fun_jac(x_middle, y_middle, p)
dbc_dya, dbc_dyb, dbc_dp = sl_bc_jac(y[:, 0], y[:, -1], p)
J = construct_global_jac(n, m, k, i_jac, j_jac, h, df_dy, df_dy_middle,
df_dp, df_dp_middle, dbc_dya, dbc_dyb, dbc_dp)
J = J.toarray()
def J_block(h, p):
return np.array([
[h**2*p**2/12 - 1, -0.5*h, -h**2*p**2/12 + 1, -0.5*h],
[0.5*h*p**2, h**2*p**2/12 - 1, 0.5*h*p**2, 1 - h**2*p**2/12]
])
J_true = np.zeros((m * n + k, m * n + k))
for i in range(m - 1):
J_true[i * n: (i + 1) * n, i * n: (i + 2) * n] = J_block(h[i], p[0])
J_true[:(m - 1) * n:2, -1] = p * h**2/6 * (y[0, :-1] - y[0, 1:])
J_true[1:(m - 1) * n:2, -1] = p * (h * (y[0, :-1] + y[0, 1:]) +
h**2/6 * (y[1, :-1] - y[1, 1:]))
J_true[8, 0] = 1
J_true[9, 8] = 1
J_true[10, 1] = 1
J_true[10, 10] = -1
assert_allclose(J, J_true, rtol=1e-10)
df_dy, df_dp = estimate_fun_jac(sl_fun, x, y, p)
df_dy_middle, df_dp_middle = estimate_fun_jac(sl_fun, x_middle, y_middle, p)
dbc_dya, dbc_dyb, dbc_dp = estimate_bc_jac(sl_bc, y[:, 0], y[:, -1], p)
J = construct_global_jac(n, m, k, i_jac, j_jac, h, df_dy, df_dy_middle,
df_dp, df_dp_middle, dbc_dya, dbc_dyb, dbc_dp)
J = J.toarray()
assert_allclose(J, J_true, rtol=1e-8, atol=1e-9)
def test_parameter_validation():
x = [0, 1, 0.5]
y = np.zeros((2, 3))
assert_raises(ValueError, solve_bvp, exp_fun, exp_bc, x, y)
x = np.linspace(0, 1, 5)
y = np.zeros((2, 4))
assert_raises(ValueError, solve_bvp, exp_fun, exp_bc, x, y)
fun = lambda x, y, p: exp_fun(x, y)
bc = lambda ya, yb, p: exp_bc(ya, yb)
y = np.zeros((2, x.shape[0]))
assert_raises(ValueError, solve_bvp, fun, bc, x, y, p=[1])
def wrong_shape_fun(x, y):
return np.zeros(3)
assert_raises(ValueError, solve_bvp, wrong_shape_fun, bc, x, y)
S = np.array([[0, 0]])
assert_raises(ValueError, solve_bvp, exp_fun, exp_bc, x, y, S=S)
def test_no_params():
x = np.linspace(0, 1, 5)
x_test = np.linspace(0, 1, 100)
y = np.zeros((2, x.shape[0]))
for fun_jac in [None, exp_fun_jac]:
for bc_jac in [None, exp_bc_jac]:
sol = solve_bvp(exp_fun, exp_bc, x, y, fun_jac=fun_jac,
bc_jac=bc_jac)
assert_equal(sol.status, 0)
assert_(sol.success)
assert_equal(sol.x.size, 5)
sol_test = sol.sol(x_test)
assert_allclose(sol_test[0], exp_sol(x_test), atol=1e-5)
f_test = exp_fun(x_test, sol_test)
r = sol.sol(x_test, 1) - f_test
rel_res = r / (1 + np.abs(f_test))
norm_res = np.sum(rel_res**2, axis=0)**0.5
assert_(np.all(norm_res < 1e-3))
assert_(np.all(sol.rms_residuals < 1e-3))
assert_allclose(sol.sol(sol.x), sol.y, rtol=1e-10, atol=1e-10)
assert_allclose(sol.sol(sol.x, 1), sol.yp, rtol=1e-10, atol=1e-10)
def test_with_params():
x = np.linspace(0, np.pi, 5)
x_test = np.linspace(0, np.pi, 100)
y = np.ones((2, x.shape[0]))
for fun_jac in [None, sl_fun_jac]:
for bc_jac in [None, sl_bc_jac]:
sol = solve_bvp(sl_fun, sl_bc, x, y, p=[0.5], fun_jac=fun_jac,
bc_jac=bc_jac)
assert_equal(sol.status, 0)
assert_(sol.success)
assert_(sol.x.size < 10)
assert_allclose(sol.p, [1], rtol=1e-4)
sol_test = sol.sol(x_test)
assert_allclose(sol_test[0], sl_sol(x_test, [1]),
rtol=1e-4, atol=1e-4)
f_test = sl_fun(x_test, sol_test, [1])
r = sol.sol(x_test, 1) - f_test
rel_res = r / (1 + np.abs(f_test))
norm_res = np.sum(rel_res ** 2, axis=0) ** 0.5
assert_(np.all(norm_res < 1e-3))
assert_(np.all(sol.rms_residuals < 1e-3))
assert_allclose(sol.sol(sol.x), sol.y, rtol=1e-10, atol=1e-10)
assert_allclose(sol.sol(sol.x, 1), sol.yp, rtol=1e-10, atol=1e-10)
def test_singular_term():
x = np.linspace(0, 1, 10)
x_test = np.linspace(0.05, 1, 100)
y = np.empty((2, 10))
y[0] = (3/4)**0.5
y[1] = 1e-4
S = np.array([[0, 0], [0, -2]])
for fun_jac in [None, emden_fun_jac]:
for bc_jac in [None, emden_bc_jac]:
sol = solve_bvp(emden_fun, emden_bc, x, y, S=S, fun_jac=fun_jac,
bc_jac=bc_jac)
assert_equal(sol.status, 0)
assert_(sol.success)
assert_equal(sol.x.size, 10)
sol_test = sol.sol(x_test)
assert_allclose(sol_test[0], emden_sol(x_test), atol=1e-5)
f_test = emden_fun(x_test, sol_test) + S.dot(sol_test) / x_test
r = sol.sol(x_test, 1) - f_test
rel_res = r / (1 + np.abs(f_test))
norm_res = np.sum(rel_res ** 2, axis=0) ** 0.5
assert_(np.all(norm_res < 1e-3))
assert_allclose(sol.sol(sol.x), sol.y, rtol=1e-10, atol=1e-10)
assert_allclose(sol.sol(sol.x, 1), sol.yp, rtol=1e-10, atol=1e-10)
def test_complex():
# The test is essentially the same as test_no_params, but boundary
# conditions are turned into complex.
x = np.linspace(0, 1, 5)
x_test = np.linspace(0, 1, 100)
y = np.zeros((2, x.shape[0]), dtype=complex)
for fun_jac in [None, exp_fun_jac]:
for bc_jac in [None, exp_bc_jac]:
sol = solve_bvp(exp_fun, exp_bc_complex, x, y, fun_jac=fun_jac,
bc_jac=bc_jac)
assert_equal(sol.status, 0)
assert_(sol.success)
sol_test = sol.sol(x_test)
assert_allclose(sol_test[0].real, exp_sol(x_test), atol=1e-5)
assert_allclose(sol_test[0].imag, exp_sol(x_test), atol=1e-5)
f_test = exp_fun(x_test, sol_test)
r = sol.sol(x_test, 1) - f_test
rel_res = r / (1 + np.abs(f_test))
norm_res = np.sum(np.real(rel_res * np.conj(rel_res)),
axis=0) ** 0.5
assert_(np.all(norm_res < 1e-3))
assert_(np.all(sol.rms_residuals < 1e-3))
assert_allclose(sol.sol(sol.x), sol.y, rtol=1e-10, atol=1e-10)
assert_allclose(sol.sol(sol.x, 1), sol.yp, rtol=1e-10, atol=1e-10)
def test_failures():
x = np.linspace(0, 1, 2)
y = np.zeros((2, x.size))
res = solve_bvp(exp_fun, exp_bc, x, y, tol=1e-5, max_nodes=5)
assert_equal(res.status, 1)
assert_(not res.success)
x = np.linspace(0, 1, 5)
y = np.zeros((2, x.size))
res = solve_bvp(undefined_fun, undefined_bc, x, y)
assert_equal(res.status, 2)
assert_(not res.success)
def test_big_problem():
n = 30
x = np.linspace(0, 1, 5)
y = np.zeros((2 * n, x.size))
sol = solve_bvp(big_fun, big_bc, x, y)
assert_equal(sol.status, 0)
assert_(sol.success)
sol_test = sol.sol(x)
assert_allclose(sol_test[0], big_sol(x, n))
f_test = big_fun(x, sol_test)
r = sol.sol(x, 1) - f_test
rel_res = r / (1 + np.abs(f_test))
norm_res = np.sum(np.real(rel_res * np.conj(rel_res)), axis=0) ** 0.5
assert_(np.all(norm_res < 1e-3))
assert_(np.all(sol.rms_residuals < 1e-3))
assert_allclose(sol.sol(sol.x), sol.y, rtol=1e-10, atol=1e-10)
assert_allclose(sol.sol(sol.x, 1), sol.yp, rtol=1e-10, atol=1e-10)
def test_shock_layer():
x = np.linspace(-1, 1, 5)
x_test = np.linspace(-1, 1, 100)
y = np.zeros((2, x.size))
sol = solve_bvp(shock_fun, shock_bc, x, y)
assert_equal(sol.status, 0)
assert_(sol.success)
assert_(sol.x.size < 110)
sol_test = sol.sol(x_test)
assert_allclose(sol_test[0], shock_sol(x_test), rtol=1e-5, atol=1e-5)
f_test = shock_fun(x_test, sol_test)
r = sol.sol(x_test, 1) - f_test
rel_res = r / (1 + np.abs(f_test))
norm_res = np.sum(rel_res ** 2, axis=0) ** 0.5
assert_(np.all(norm_res < 1e-3))
assert_allclose(sol.sol(sol.x), sol.y, rtol=1e-10, atol=1e-10)
assert_allclose(sol.sol(sol.x, 1), sol.yp, rtol=1e-10, atol=1e-10)
def test_nonlin_bc():
x = np.linspace(0, 0.1, 5)
x_test = x
y = np.zeros([2, x.size])
sol = solve_bvp(nonlin_bc_fun, nonlin_bc_bc, x, y)
assert_equal(sol.status, 0)
assert_(sol.success)
assert_(sol.x.size < 8)
sol_test = sol.sol(x_test)
assert_allclose(sol_test[0], nonlin_bc_sol(x_test), rtol=1e-5, atol=1e-5)
f_test = nonlin_bc_fun(x_test, sol_test)
r = sol.sol(x_test, 1) - f_test
rel_res = r / (1 + np.abs(f_test))
norm_res = np.sum(rel_res ** 2, axis=0) ** 0.5
assert_(np.all(norm_res < 1e-3))
assert_allclose(sol.sol(sol.x), sol.y, rtol=1e-10, atol=1e-10)
assert_allclose(sol.sol(sol.x, 1), sol.yp, rtol=1e-10, atol=1e-10)
def test_verbose():
# Smoke test that checks the printing does something and does not crash
x = np.linspace(0, 1, 5)
y = np.zeros((2, x.shape[0]))
for verbose in [0, 1, 2]:
old_stdout = sys.stdout
sys.stdout = StringIO()
try:
sol = solve_bvp(exp_fun, exp_bc, x, y, verbose=verbose)
text = sys.stdout.getvalue()
finally:
sys.stdout = old_stdout
assert_(sol.success)
if verbose == 0:
assert_(not text, text)
if verbose >= 1:
assert_("Solved in" in text, text)
if verbose >= 2:
assert_("Max residual" in text, text)

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@ -0,0 +1,830 @@
# Authors: Nils Wagner, Ed Schofield, Pauli Virtanen, John Travers
"""
Tests for numerical integration.
"""
import numpy as np
from numpy import (arange, zeros, array, dot, sqrt, cos, sin, eye, pi, exp,
allclose)
from numpy.testing import (
assert_, assert_array_almost_equal,
assert_allclose, assert_array_equal, assert_equal, assert_warns)
from pytest import raises as assert_raises
from scipy.integrate import odeint, ode, complex_ode
#------------------------------------------------------------------------------
# Test ODE integrators
#------------------------------------------------------------------------------
class TestOdeint(object):
# Check integrate.odeint
def _do_problem(self, problem):
t = arange(0.0, problem.stop_t, 0.05)
# Basic case
z, infodict = odeint(problem.f, problem.z0, t, full_output=True)
assert_(problem.verify(z, t))
# Use tfirst=True
z, infodict = odeint(lambda t, y: problem.f(y, t), problem.z0, t,
full_output=True, tfirst=True)
assert_(problem.verify(z, t))
if hasattr(problem, 'jac'):
# Use Dfun
z, infodict = odeint(problem.f, problem.z0, t, Dfun=problem.jac,
full_output=True)
assert_(problem.verify(z, t))
# Use Dfun and tfirst=True
z, infodict = odeint(lambda t, y: problem.f(y, t), problem.z0, t,
Dfun=lambda t, y: problem.jac(y, t),
full_output=True, tfirst=True)
assert_(problem.verify(z, t))
def test_odeint(self):
for problem_cls in PROBLEMS:
problem = problem_cls()
if problem.cmplx:
continue
self._do_problem(problem)
class TestODEClass(object):
ode_class = None # Set in subclass.
def _do_problem(self, problem, integrator, method='adams'):
# ode has callback arguments in different order than odeint
f = lambda t, z: problem.f(z, t)
jac = None
if hasattr(problem, 'jac'):
jac = lambda t, z: problem.jac(z, t)
integrator_params = {}
if problem.lband is not None or problem.uband is not None:
integrator_params['uband'] = problem.uband
integrator_params['lband'] = problem.lband
ig = self.ode_class(f, jac)
ig.set_integrator(integrator,
atol=problem.atol/10,
rtol=problem.rtol/10,
method=method,
**integrator_params)
ig.set_initial_value(problem.z0, t=0.0)
z = ig.integrate(problem.stop_t)
assert_array_equal(z, ig.y)
assert_(ig.successful(), (problem, method))
assert_(ig.get_return_code() > 0, (problem, method))
assert_(problem.verify(array([z]), problem.stop_t), (problem, method))
class TestOde(TestODEClass):
ode_class = ode
def test_vode(self):
# Check the vode solver
for problem_cls in PROBLEMS:
problem = problem_cls()
if problem.cmplx:
continue
if not problem.stiff:
self._do_problem(problem, 'vode', 'adams')
self._do_problem(problem, 'vode', 'bdf')
def test_zvode(self):
# Check the zvode solver
for problem_cls in PROBLEMS:
problem = problem_cls()
if not problem.stiff:
self._do_problem(problem, 'zvode', 'adams')
self._do_problem(problem, 'zvode', 'bdf')
def test_lsoda(self):
# Check the lsoda solver
for problem_cls in PROBLEMS:
problem = problem_cls()
if problem.cmplx:
continue
self._do_problem(problem, 'lsoda')
def test_dopri5(self):
# Check the dopri5 solver
for problem_cls in PROBLEMS:
problem = problem_cls()
if problem.cmplx:
continue
if problem.stiff:
continue
if hasattr(problem, 'jac'):
continue
self._do_problem(problem, 'dopri5')
def test_dop853(self):
# Check the dop853 solver
for problem_cls in PROBLEMS:
problem = problem_cls()
if problem.cmplx:
continue
if problem.stiff:
continue
if hasattr(problem, 'jac'):
continue
self._do_problem(problem, 'dop853')
def test_concurrent_fail(self):
for sol in ('vode', 'zvode', 'lsoda'):
f = lambda t, y: 1.0
r = ode(f).set_integrator(sol)
r.set_initial_value(0, 0)
r2 = ode(f).set_integrator(sol)
r2.set_initial_value(0, 0)
r.integrate(r.t + 0.1)
r2.integrate(r2.t + 0.1)
assert_raises(RuntimeError, r.integrate, r.t + 0.1)
def test_concurrent_ok(self):
f = lambda t, y: 1.0
for k in range(3):
for sol in ('vode', 'zvode', 'lsoda', 'dopri5', 'dop853'):
r = ode(f).set_integrator(sol)
r.set_initial_value(0, 0)
r2 = ode(f).set_integrator(sol)
r2.set_initial_value(0, 0)
r.integrate(r.t + 0.1)
r2.integrate(r2.t + 0.1)
r2.integrate(r2.t + 0.1)
assert_allclose(r.y, 0.1)
assert_allclose(r2.y, 0.2)
for sol in ('dopri5', 'dop853'):
r = ode(f).set_integrator(sol)
r.set_initial_value(0, 0)
r2 = ode(f).set_integrator(sol)
r2.set_initial_value(0, 0)
r.integrate(r.t + 0.1)
r.integrate(r.t + 0.1)
r2.integrate(r2.t + 0.1)
r.integrate(r.t + 0.1)
r2.integrate(r2.t + 0.1)
assert_allclose(r.y, 0.3)
assert_allclose(r2.y, 0.2)
class TestComplexOde(TestODEClass):
ode_class = complex_ode
def test_vode(self):
# Check the vode solver
for problem_cls in PROBLEMS:
problem = problem_cls()
if not problem.stiff:
self._do_problem(problem, 'vode', 'adams')
else:
self._do_problem(problem, 'vode', 'bdf')
def test_lsoda(self):
# Check the lsoda solver
for problem_cls in PROBLEMS:
problem = problem_cls()
self._do_problem(problem, 'lsoda')
def test_dopri5(self):
# Check the dopri5 solver
for problem_cls in PROBLEMS:
problem = problem_cls()
if problem.stiff:
continue
if hasattr(problem, 'jac'):
continue
self._do_problem(problem, 'dopri5')
def test_dop853(self):
# Check the dop853 solver
for problem_cls in PROBLEMS:
problem = problem_cls()
if problem.stiff:
continue
if hasattr(problem, 'jac'):
continue
self._do_problem(problem, 'dop853')
class TestSolout(object):
# Check integrate.ode correctly handles solout for dopri5 and dop853
def _run_solout_test(self, integrator):
# Check correct usage of solout
ts = []
ys = []
t0 = 0.0
tend = 10.0
y0 = [1.0, 2.0]
def solout(t, y):
ts.append(t)
ys.append(y.copy())
def rhs(t, y):
return [y[0] + y[1], -y[1]**2]
ig = ode(rhs).set_integrator(integrator)
ig.set_solout(solout)
ig.set_initial_value(y0, t0)
ret = ig.integrate(tend)
assert_array_equal(ys[0], y0)
assert_array_equal(ys[-1], ret)
assert_equal(ts[0], t0)
assert_equal(ts[-1], tend)
def test_solout(self):
for integrator in ('dopri5', 'dop853'):
self._run_solout_test(integrator)
def _run_solout_after_initial_test(self, integrator):
# Check if solout works even if it is set after the initial value.
ts = []
ys = []
t0 = 0.0
tend = 10.0
y0 = [1.0, 2.0]
def solout(t, y):
ts.append(t)
ys.append(y.copy())
def rhs(t, y):
return [y[0] + y[1], -y[1]**2]
ig = ode(rhs).set_integrator(integrator)
ig.set_initial_value(y0, t0)
ig.set_solout(solout)
ret = ig.integrate(tend)
assert_array_equal(ys[0], y0)
assert_array_equal(ys[-1], ret)
assert_equal(ts[0], t0)
assert_equal(ts[-1], tend)
def test_solout_after_initial(self):
for integrator in ('dopri5', 'dop853'):
self._run_solout_after_initial_test(integrator)
def _run_solout_break_test(self, integrator):
# Check correct usage of stopping via solout
ts = []
ys = []
t0 = 0.0
tend = 10.0
y0 = [1.0, 2.0]
def solout(t, y):
ts.append(t)
ys.append(y.copy())
if t > tend/2.0:
return -1
def rhs(t, y):
return [y[0] + y[1], -y[1]**2]
ig = ode(rhs).set_integrator(integrator)
ig.set_solout(solout)
ig.set_initial_value(y0, t0)
ret = ig.integrate(tend)
assert_array_equal(ys[0], y0)
assert_array_equal(ys[-1], ret)
assert_equal(ts[0], t0)
assert_(ts[-1] > tend/2.0)
assert_(ts[-1] < tend)
def test_solout_break(self):
for integrator in ('dopri5', 'dop853'):
self._run_solout_break_test(integrator)
class TestComplexSolout(object):
# Check integrate.ode correctly handles solout for dopri5 and dop853
def _run_solout_test(self, integrator):
# Check correct usage of solout
ts = []
ys = []
t0 = 0.0
tend = 20.0
y0 = [0.0]
def solout(t, y):
ts.append(t)
ys.append(y.copy())
def rhs(t, y):
return [1.0/(t - 10.0 - 1j)]
ig = complex_ode(rhs).set_integrator(integrator)
ig.set_solout(solout)
ig.set_initial_value(y0, t0)
ret = ig.integrate(tend)
assert_array_equal(ys[0], y0)
assert_array_equal(ys[-1], ret)
assert_equal(ts[0], t0)
assert_equal(ts[-1], tend)
def test_solout(self):
for integrator in ('dopri5', 'dop853'):
self._run_solout_test(integrator)
def _run_solout_break_test(self, integrator):
# Check correct usage of stopping via solout
ts = []
ys = []
t0 = 0.0
tend = 20.0
y0 = [0.0]
def solout(t, y):
ts.append(t)
ys.append(y.copy())
if t > tend/2.0:
return -1
def rhs(t, y):
return [1.0/(t - 10.0 - 1j)]
ig = complex_ode(rhs).set_integrator(integrator)
ig.set_solout(solout)
ig.set_initial_value(y0, t0)
ret = ig.integrate(tend)
assert_array_equal(ys[0], y0)
assert_array_equal(ys[-1], ret)
assert_equal(ts[0], t0)
assert_(ts[-1] > tend/2.0)
assert_(ts[-1] < tend)
def test_solout_break(self):
for integrator in ('dopri5', 'dop853'):
self._run_solout_break_test(integrator)
#------------------------------------------------------------------------------
# Test problems
#------------------------------------------------------------------------------
class ODE:
"""
ODE problem
"""
stiff = False
cmplx = False
stop_t = 1
z0 = []
lband = None
uband = None
atol = 1e-6
rtol = 1e-5
class SimpleOscillator(ODE):
r"""
Free vibration of a simple oscillator::
m \ddot{u} + k u = 0, u(0) = u_0 \dot{u}(0) \dot{u}_0
Solution::
u(t) = u_0*cos(sqrt(k/m)*t)+\dot{u}_0*sin(sqrt(k/m)*t)/sqrt(k/m)
"""
stop_t = 1 + 0.09
z0 = array([1.0, 0.1], float)
k = 4.0
m = 1.0
def f(self, z, t):
tmp = zeros((2, 2), float)
tmp[0, 1] = 1.0
tmp[1, 0] = -self.k / self.m
return dot(tmp, z)
def verify(self, zs, t):
omega = sqrt(self.k / self.m)
u = self.z0[0]*cos(omega*t) + self.z0[1]*sin(omega*t)/omega
return allclose(u, zs[:, 0], atol=self.atol, rtol=self.rtol)
class ComplexExp(ODE):
r"""The equation :lm:`\dot u = i u`"""
stop_t = 1.23*pi
z0 = exp([1j, 2j, 3j, 4j, 5j])
cmplx = True
def f(self, z, t):
return 1j*z
def jac(self, z, t):
return 1j*eye(5)
def verify(self, zs, t):
u = self.z0 * exp(1j*t)
return allclose(u, zs, atol=self.atol, rtol=self.rtol)
class Pi(ODE):
r"""Integrate 1/(t + 1j) from t=-10 to t=10"""
stop_t = 20
z0 = [0]
cmplx = True
def f(self, z, t):
return array([1./(t - 10 + 1j)])
def verify(self, zs, t):
u = -2j * np.arctan(10)
return allclose(u, zs[-1, :], atol=self.atol, rtol=self.rtol)
class CoupledDecay(ODE):
r"""
3 coupled decays suited for banded treatment
(banded mode makes it necessary when N>>3)
"""
stiff = True
stop_t = 0.5
z0 = [5.0, 7.0, 13.0]
lband = 1
uband = 0
lmbd = [0.17, 0.23, 0.29] # fictitious decay constants
def f(self, z, t):
lmbd = self.lmbd
return np.array([-lmbd[0]*z[0],
-lmbd[1]*z[1] + lmbd[0]*z[0],
-lmbd[2]*z[2] + lmbd[1]*z[1]])
def jac(self, z, t):
# The full Jacobian is
#
# [-lmbd[0] 0 0 ]
# [ lmbd[0] -lmbd[1] 0 ]
# [ 0 lmbd[1] -lmbd[2]]
#
# The lower and upper bandwidths are lband=1 and uband=0, resp.
# The representation of this array in packed format is
#
# [-lmbd[0] -lmbd[1] -lmbd[2]]
# [ lmbd[0] lmbd[1] 0 ]
lmbd = self.lmbd
j = np.zeros((self.lband + self.uband + 1, 3), order='F')
def set_j(ri, ci, val):
j[self.uband + ri - ci, ci] = val
set_j(0, 0, -lmbd[0])
set_j(1, 0, lmbd[0])
set_j(1, 1, -lmbd[1])
set_j(2, 1, lmbd[1])
set_j(2, 2, -lmbd[2])
return j
def verify(self, zs, t):
# Formulae derived by hand
lmbd = np.array(self.lmbd)
d10 = lmbd[1] - lmbd[0]
d21 = lmbd[2] - lmbd[1]
d20 = lmbd[2] - lmbd[0]
e0 = np.exp(-lmbd[0] * t)
e1 = np.exp(-lmbd[1] * t)
e2 = np.exp(-lmbd[2] * t)
u = np.vstack((
self.z0[0] * e0,
self.z0[1] * e1 + self.z0[0] * lmbd[0] / d10 * (e0 - e1),
self.z0[2] * e2 + self.z0[1] * lmbd[1] / d21 * (e1 - e2) +
lmbd[1] * lmbd[0] * self.z0[0] / d10 *
(1 / d20 * (e0 - e2) - 1 / d21 * (e1 - e2)))).transpose()
return allclose(u, zs, atol=self.atol, rtol=self.rtol)
PROBLEMS = [SimpleOscillator, ComplexExp, Pi, CoupledDecay]
#------------------------------------------------------------------------------
def f(t, x):
dxdt = [x[1], -x[0]]
return dxdt
def jac(t, x):
j = array([[0.0, 1.0],
[-1.0, 0.0]])
return j
def f1(t, x, omega):
dxdt = [omega*x[1], -omega*x[0]]
return dxdt
def jac1(t, x, omega):
j = array([[0.0, omega],
[-omega, 0.0]])
return j
def f2(t, x, omega1, omega2):
dxdt = [omega1*x[1], -omega2*x[0]]
return dxdt
def jac2(t, x, omega1, omega2):
j = array([[0.0, omega1],
[-omega2, 0.0]])
return j
def fv(t, x, omega):
dxdt = [omega[0]*x[1], -omega[1]*x[0]]
return dxdt
def jacv(t, x, omega):
j = array([[0.0, omega[0]],
[-omega[1], 0.0]])
return j
class ODECheckParameterUse(object):
"""Call an ode-class solver with several cases of parameter use."""
# solver_name must be set before tests can be run with this class.
# Set these in subclasses.
solver_name = ''
solver_uses_jac = False
def _get_solver(self, f, jac):
solver = ode(f, jac)
if self.solver_uses_jac:
solver.set_integrator(self.solver_name, atol=1e-9, rtol=1e-7,
with_jacobian=self.solver_uses_jac)
else:
# XXX Shouldn't set_integrator *always* accept the keyword arg
# 'with_jacobian', and perhaps raise an exception if it is set
# to True if the solver can't actually use it?
solver.set_integrator(self.solver_name, atol=1e-9, rtol=1e-7)
return solver
def _check_solver(self, solver):
ic = [1.0, 0.0]
solver.set_initial_value(ic, 0.0)
solver.integrate(pi)
assert_array_almost_equal(solver.y, [-1.0, 0.0])
def test_no_params(self):
solver = self._get_solver(f, jac)
self._check_solver(solver)
def test_one_scalar_param(self):
solver = self._get_solver(f1, jac1)
omega = 1.0
solver.set_f_params(omega)
if self.solver_uses_jac:
solver.set_jac_params(omega)
self._check_solver(solver)
def test_two_scalar_params(self):
solver = self._get_solver(f2, jac2)
omega1 = 1.0
omega2 = 1.0
solver.set_f_params(omega1, omega2)
if self.solver_uses_jac:
solver.set_jac_params(omega1, omega2)
self._check_solver(solver)
def test_vector_param(self):
solver = self._get_solver(fv, jacv)
omega = [1.0, 1.0]
solver.set_f_params(omega)
if self.solver_uses_jac:
solver.set_jac_params(omega)
self._check_solver(solver)
def test_warns_on_failure(self):
# Set nsteps small to ensure failure
solver = self._get_solver(f, jac)
solver.set_integrator(self.solver_name, nsteps=1)
ic = [1.0, 0.0]
solver.set_initial_value(ic, 0.0)
assert_warns(UserWarning, solver.integrate, pi)
class TestDOPRI5CheckParameterUse(ODECheckParameterUse):
solver_name = 'dopri5'
solver_uses_jac = False
class TestDOP853CheckParameterUse(ODECheckParameterUse):
solver_name = 'dop853'
solver_uses_jac = False
class TestVODECheckParameterUse(ODECheckParameterUse):
solver_name = 'vode'
solver_uses_jac = True
class TestZVODECheckParameterUse(ODECheckParameterUse):
solver_name = 'zvode'
solver_uses_jac = True
class TestLSODACheckParameterUse(ODECheckParameterUse):
solver_name = 'lsoda'
solver_uses_jac = True
def test_odeint_trivial_time():
# Test that odeint succeeds when given a single time point
# and full_output=True. This is a regression test for gh-4282.
y0 = 1
t = [0]
y, info = odeint(lambda y, t: -y, y0, t, full_output=True)
assert_array_equal(y, np.array([[y0]]))
def test_odeint_banded_jacobian():
# Test the use of the `Dfun`, `ml` and `mu` options of odeint.
def func(y, t, c):
return c.dot(y)
def jac(y, t, c):
return c
def jac_transpose(y, t, c):
return c.T.copy(order='C')
def bjac_rows(y, t, c):
jac = np.row_stack((np.r_[0, np.diag(c, 1)],
np.diag(c),
np.r_[np.diag(c, -1), 0],
np.r_[np.diag(c, -2), 0, 0]))
return jac
def bjac_cols(y, t, c):
return bjac_rows(y, t, c).T.copy(order='C')
c = array([[-205, 0.01, 0.00, 0.0],
[0.1, -2.50, 0.02, 0.0],
[1e-3, 0.01, -2.0, 0.01],
[0.00, 0.00, 0.1, -1.0]])
y0 = np.ones(4)
t = np.array([0, 5, 10, 100])
# Use the full Jacobian.
sol1, info1 = odeint(func, y0, t, args=(c,), full_output=True,
atol=1e-13, rtol=1e-11, mxstep=10000,
Dfun=jac)
# Use the transposed full Jacobian, with col_deriv=True.
sol2, info2 = odeint(func, y0, t, args=(c,), full_output=True,
atol=1e-13, rtol=1e-11, mxstep=10000,
Dfun=jac_transpose, col_deriv=True)
# Use the banded Jacobian.
sol3, info3 = odeint(func, y0, t, args=(c,), full_output=True,
atol=1e-13, rtol=1e-11, mxstep=10000,
Dfun=bjac_rows, ml=2, mu=1)
# Use the transposed banded Jacobian, with col_deriv=True.
sol4, info4 = odeint(func, y0, t, args=(c,), full_output=True,
atol=1e-13, rtol=1e-11, mxstep=10000,
Dfun=bjac_cols, ml=2, mu=1, col_deriv=True)
assert_allclose(sol1, sol2, err_msg="sol1 != sol2")
assert_allclose(sol1, sol3, atol=1e-12, err_msg="sol1 != sol3")
assert_allclose(sol3, sol4, err_msg="sol3 != sol4")
# Verify that the number of jacobian evaluations was the same for the
# calls of odeint with a full jacobian and with a banded jacobian. This is
# a regression test--there was a bug in the handling of banded jacobians
# that resulted in an incorrect jacobian matrix being passed to the LSODA
# code. That would cause errors or excessive jacobian evaluations.
assert_array_equal(info1['nje'], info2['nje'])
assert_array_equal(info3['nje'], info4['nje'])
# Test the use of tfirst
sol1ty, info1ty = odeint(lambda t, y, c: func(y, t, c), y0, t, args=(c,),
full_output=True, atol=1e-13, rtol=1e-11,
mxstep=10000,
Dfun=lambda t, y, c: jac(y, t, c), tfirst=True)
# The code should execute the exact same sequence of floating point
# calculations, so these should be exactly equal. We'll be safe and use
# a small tolerance.
assert_allclose(sol1, sol1ty, rtol=1e-12, err_msg="sol1 != sol1ty")
def test_odeint_errors():
def sys1d(x, t):
return -100*x
def bad1(x, t):
return 1.0/0
def bad2(x, t):
return "foo"
def bad_jac1(x, t):
return 1.0/0
def bad_jac2(x, t):
return [["foo"]]
def sys2d(x, t):
return [-100*x[0], -0.1*x[1]]
def sys2d_bad_jac(x, t):
return [[1.0/0, 0], [0, -0.1]]
assert_raises(ZeroDivisionError, odeint, bad1, 1.0, [0, 1])
assert_raises(ValueError, odeint, bad2, 1.0, [0, 1])
assert_raises(ZeroDivisionError, odeint, sys1d, 1.0, [0, 1], Dfun=bad_jac1)
assert_raises(ValueError, odeint, sys1d, 1.0, [0, 1], Dfun=bad_jac2)
assert_raises(ZeroDivisionError, odeint, sys2d, [1.0, 1.0], [0, 1],
Dfun=sys2d_bad_jac)
def test_odeint_bad_shapes():
# Tests of some errors that can occur with odeint.
def badrhs(x, t):
return [1, -1]
def sys1(x, t):
return -100*x
def badjac(x, t):
return [[0, 0, 0]]
# y0 must be at most 1-d.
bad_y0 = [[0, 0], [0, 0]]
assert_raises(ValueError, odeint, sys1, bad_y0, [0, 1])
# t must be at most 1-d.
bad_t = [[0, 1], [2, 3]]
assert_raises(ValueError, odeint, sys1, [10.0], bad_t)
# y0 is 10, but badrhs(x, t) returns [1, -1].
assert_raises(RuntimeError, odeint, badrhs, 10, [0, 1])
# shape of array returned by badjac(x, t) is not correct.
assert_raises(RuntimeError, odeint, sys1, [10, 10], [0, 1], Dfun=badjac)
def test_repeated_t_values():
"""Regression test for gh-8217."""
def func(x, t):
return -0.25*x
t = np.zeros(10)
sol = odeint(func, [1.], t)
assert_array_equal(sol, np.ones((len(t), 1)))
tau = 4*np.log(2)
t = [0]*9 + [tau, 2*tau, 2*tau, 3*tau]
sol = odeint(func, [1, 2], t, rtol=1e-12, atol=1e-12)
expected_sol = np.array([[1.0, 2.0]]*9 +
[[0.5, 1.0],
[0.25, 0.5],
[0.25, 0.5],
[0.125, 0.25]])
assert_allclose(sol, expected_sol)
# Edge case: empty t sequence.
sol = odeint(func, [1.], [])
assert_array_equal(sol, np.array([], dtype=np.float64).reshape((0, 1)))
# t values are not monotonic.
assert_raises(ValueError, odeint, func, [1.], [0, 1, 0.5, 0])
assert_raises(ValueError, odeint, func, [1, 2, 3], [0, -1, -2, 3])

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@ -0,0 +1,75 @@
import numpy as np
from numpy.testing import assert_equal, assert_allclose
from scipy.integrate import odeint
import scipy.integrate._test_odeint_banded as banded5x5
def rhs(y, t):
dydt = np.zeros_like(y)
banded5x5.banded5x5(t, y, dydt)
return dydt
def jac(y, t):
n = len(y)
jac = np.zeros((n, n), order='F')
banded5x5.banded5x5_jac(t, y, 1, 1, jac)
return jac
def bjac(y, t):
n = len(y)
bjac = np.zeros((4, n), order='F')
banded5x5.banded5x5_bjac(t, y, 1, 1, bjac)
return bjac
JACTYPE_FULL = 1
JACTYPE_BANDED = 4
def check_odeint(jactype):
if jactype == JACTYPE_FULL:
ml = None
mu = None
jacobian = jac
elif jactype == JACTYPE_BANDED:
ml = 2
mu = 1
jacobian = bjac
else:
raise ValueError("invalid jactype: %r" % (jactype,))
y0 = np.arange(1.0, 6.0)
# These tolerances must match the tolerances used in banded5x5.f.
rtol = 1e-11
atol = 1e-13
dt = 0.125
nsteps = 64
t = dt * np.arange(nsteps+1)
sol, info = odeint(rhs, y0, t,
Dfun=jacobian, ml=ml, mu=mu,
atol=atol, rtol=rtol, full_output=True)
yfinal = sol[-1]
odeint_nst = info['nst'][-1]
odeint_nfe = info['nfe'][-1]
odeint_nje = info['nje'][-1]
y1 = y0.copy()
# Pure Fortran solution. y1 is modified in-place.
nst, nfe, nje = banded5x5.banded5x5_solve(y1, nsteps, dt, jactype)
# It is likely that yfinal and y1 are *exactly* the same, but
# we'll be cautious and use assert_allclose.
assert_allclose(yfinal, y1, rtol=1e-12)
assert_equal((odeint_nst, odeint_nfe, odeint_nje), (nst, nfe, nje))
def test_odeint_full_jac():
check_odeint(JACTYPE_FULL)
def test_odeint_banded_jac():
check_odeint(JACTYPE_BANDED)

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import sys
import math
import numpy as np
from numpy import sqrt, cos, sin, arctan, exp, log, pi, Inf
from numpy.testing import (assert_,
assert_allclose, assert_array_less, assert_almost_equal)
import pytest
from scipy.integrate import quad, dblquad, tplquad, nquad
from scipy._lib._ccallback import LowLevelCallable
import ctypes
import ctypes.util
from scipy._lib._ccallback_c import sine_ctypes
import scipy.integrate._test_multivariate as clib_test
def assert_quad(value_and_err, tabled_value, errTol=1.5e-8):
value, err = value_and_err
assert_allclose(value, tabled_value, atol=err, rtol=0)
if errTol is not None:
assert_array_less(err, errTol)
def get_clib_test_routine(name, restype, *argtypes):
ptr = getattr(clib_test, name)
return ctypes.cast(ptr, ctypes.CFUNCTYPE(restype, *argtypes))
class TestCtypesQuad(object):
def setup_method(self):
if sys.platform == 'win32':
files = ['api-ms-win-crt-math-l1-1-0.dll']
elif sys.platform == 'darwin':
files = ['libm.dylib']
else:
files = ['libm.so', 'libm.so.6']
for file in files:
try:
self.lib = ctypes.CDLL(file)
break
except OSError:
pass
else:
# This test doesn't work on some Linux platforms (Fedora for
# example) that put an ld script in libm.so - see gh-5370
pytest.skip("Ctypes can't import libm.so")
restype = ctypes.c_double
argtypes = (ctypes.c_double,)
for name in ['sin', 'cos', 'tan']:
func = getattr(self.lib, name)
func.restype = restype
func.argtypes = argtypes
def test_typical(self):
assert_quad(quad(self.lib.sin, 0, 5), quad(math.sin, 0, 5)[0])
assert_quad(quad(self.lib.cos, 0, 5), quad(math.cos, 0, 5)[0])
assert_quad(quad(self.lib.tan, 0, 1), quad(math.tan, 0, 1)[0])
def test_ctypes_sine(self):
quad(LowLevelCallable(sine_ctypes), 0, 1)
def test_ctypes_variants(self):
sin_0 = get_clib_test_routine('_sin_0', ctypes.c_double,
ctypes.c_double, ctypes.c_void_p)
sin_1 = get_clib_test_routine('_sin_1', ctypes.c_double,
ctypes.c_int, ctypes.POINTER(ctypes.c_double),
ctypes.c_void_p)
sin_2 = get_clib_test_routine('_sin_2', ctypes.c_double,
ctypes.c_double)
sin_3 = get_clib_test_routine('_sin_3', ctypes.c_double,
ctypes.c_int, ctypes.POINTER(ctypes.c_double))
sin_4 = get_clib_test_routine('_sin_3', ctypes.c_double,
ctypes.c_int, ctypes.c_double)
all_sigs = [sin_0, sin_1, sin_2, sin_3, sin_4]
legacy_sigs = [sin_2, sin_4]
legacy_only_sigs = [sin_4]
# LowLevelCallables work for new signatures
for j, func in enumerate(all_sigs):
callback = LowLevelCallable(func)
if func in legacy_only_sigs:
pytest.raises(ValueError, quad, callback, 0, pi)
else:
assert_allclose(quad(callback, 0, pi)[0], 2.0)
# Plain ctypes items work only for legacy signatures
for j, func in enumerate(legacy_sigs):
if func in legacy_sigs:
assert_allclose(quad(func, 0, pi)[0], 2.0)
else:
pytest.raises(ValueError, quad, func, 0, pi)
class TestMultivariateCtypesQuad(object):
def setup_method(self):
restype = ctypes.c_double
argtypes = (ctypes.c_int, ctypes.c_double)
for name in ['_multivariate_typical', '_multivariate_indefinite',
'_multivariate_sin']:
func = get_clib_test_routine(name, restype, *argtypes)
setattr(self, name, func)
def test_typical(self):
# 1) Typical function with two extra arguments:
assert_quad(quad(self._multivariate_typical, 0, pi, (2, 1.8)),
0.30614353532540296487)
def test_indefinite(self):
# 2) Infinite integration limits --- Euler's constant
assert_quad(quad(self._multivariate_indefinite, 0, Inf),
0.577215664901532860606512)
def test_threadsafety(self):
# Ensure multivariate ctypes are threadsafe
def threadsafety(y):
return y + quad(self._multivariate_sin, 0, 1)[0]
assert_quad(quad(threadsafety, 0, 1), 0.9596976941318602)
class TestQuad(object):
def test_typical(self):
# 1) Typical function with two extra arguments:
def myfunc(x, n, z): # Bessel function integrand
return cos(n*x-z*sin(x))/pi
assert_quad(quad(myfunc, 0, pi, (2, 1.8)), 0.30614353532540296487)
def test_indefinite(self):
# 2) Infinite integration limits --- Euler's constant
def myfunc(x): # Euler's constant integrand
return -exp(-x)*log(x)
assert_quad(quad(myfunc, 0, Inf), 0.577215664901532860606512)
def test_singular(self):
# 3) Singular points in region of integration.
def myfunc(x):
if 0 < x < 2.5:
return sin(x)
elif 2.5 <= x <= 5.0:
return exp(-x)
else:
return 0.0
assert_quad(quad(myfunc, 0, 10, points=[2.5, 5.0]),
1 - cos(2.5) + exp(-2.5) - exp(-5.0))
def test_sine_weighted_finite(self):
# 4) Sine weighted integral (finite limits)
def myfunc(x, a):
return exp(a*(x-1))
ome = 2.0**3.4
assert_quad(quad(myfunc, 0, 1, args=20, weight='sin', wvar=ome),
(20*sin(ome)-ome*cos(ome)+ome*exp(-20))/(20**2 + ome**2))
def test_sine_weighted_infinite(self):
# 5) Sine weighted integral (infinite limits)
def myfunc(x, a):
return exp(-x*a)
a = 4.0
ome = 3.0
assert_quad(quad(myfunc, 0, Inf, args=a, weight='sin', wvar=ome),
ome/(a**2 + ome**2))
def test_cosine_weighted_infinite(self):
# 6) Cosine weighted integral (negative infinite limits)
def myfunc(x, a):
return exp(x*a)
a = 2.5
ome = 2.3
assert_quad(quad(myfunc, -Inf, 0, args=a, weight='cos', wvar=ome),
a/(a**2 + ome**2))
def test_algebraic_log_weight(self):
# 6) Algebraic-logarithmic weight.
def myfunc(x, a):
return 1/(1+x+2**(-a))
a = 1.5
assert_quad(quad(myfunc, -1, 1, args=a, weight='alg',
wvar=(-0.5, -0.5)),
pi/sqrt((1+2**(-a))**2 - 1))
def test_cauchypv_weight(self):
# 7) Cauchy prinicpal value weighting w(x) = 1/(x-c)
def myfunc(x, a):
return 2.0**(-a)/((x-1)**2+4.0**(-a))
a = 0.4
tabledValue = ((2.0**(-0.4)*log(1.5) -
2.0**(-1.4)*log((4.0**(-a)+16) / (4.0**(-a)+1)) -
arctan(2.0**(a+2)) -
arctan(2.0**a)) /
(4.0**(-a) + 1))
assert_quad(quad(myfunc, 0, 5, args=0.4, weight='cauchy', wvar=2.0),
tabledValue, errTol=1.9e-8)
def test_b_less_than_a(self):
def f(x, p, q):
return p * np.exp(-q*x)
val_1, err_1 = quad(f, 0, np.inf, args=(2, 3))
val_2, err_2 = quad(f, np.inf, 0, args=(2, 3))
assert_allclose(val_1, -val_2, atol=max(err_1, err_2))
def test_b_less_than_a_2(self):
def f(x, s):
return np.exp(-x**2 / 2 / s) / np.sqrt(2.*s)
val_1, err_1 = quad(f, -np.inf, np.inf, args=(2,))
val_2, err_2 = quad(f, np.inf, -np.inf, args=(2,))
assert_allclose(val_1, -val_2, atol=max(err_1, err_2))
def test_b_less_than_a_3(self):
def f(x):
return 1.0
val_1, err_1 = quad(f, 0, 1, weight='alg', wvar=(0, 0))
val_2, err_2 = quad(f, 1, 0, weight='alg', wvar=(0, 0))
assert_allclose(val_1, -val_2, atol=max(err_1, err_2))
def test_b_less_than_a_full_output(self):
def f(x):
return 1.0
res_1 = quad(f, 0, 1, weight='alg', wvar=(0, 0), full_output=True)
res_2 = quad(f, 1, 0, weight='alg', wvar=(0, 0), full_output=True)
err = max(res_1[1], res_2[1])
assert_allclose(res_1[0], -res_2[0], atol=err)
def test_double_integral(self):
# 8) Double Integral test
def simpfunc(y, x): # Note order of arguments.
return x+y
a, b = 1.0, 2.0
assert_quad(dblquad(simpfunc, a, b, lambda x: x, lambda x: 2*x),
5/6.0 * (b**3.0-a**3.0))
def test_double_integral2(self):
def func(x0, x1, t0, t1):
return x0 + x1 + t0 + t1
g = lambda x: x
h = lambda x: 2 * x
args = 1, 2
assert_quad(dblquad(func, 1, 2, g, h, args=args),35./6 + 9*.5)
def test_double_integral3(self):
def func(x0, x1):
return x0 + x1 + 1 + 2
assert_quad(dblquad(func, 1, 2, 1, 2),6.)
def test_triple_integral(self):
# 9) Triple Integral test
def simpfunc(z, y, x, t): # Note order of arguments.
return (x+y+z)*t
a, b = 1.0, 2.0
assert_quad(tplquad(simpfunc, a, b,
lambda x: x, lambda x: 2*x,
lambda x, y: x - y, lambda x, y: x + y,
(2.,)),
2*8/3.0 * (b**4.0 - a**4.0))
class TestNQuad(object):
def test_fixed_limits(self):
def func1(x0, x1, x2, x3):
val = (x0**2 + x1*x2 - x3**3 + np.sin(x0) +
(1 if (x0 - 0.2*x3 - 0.5 - 0.25*x1 > 0) else 0))
return val
def opts_basic(*args):
return {'points': [0.2*args[2] + 0.5 + 0.25*args[0]]}
res = nquad(func1, [[0, 1], [-1, 1], [.13, .8], [-.15, 1]],
opts=[opts_basic, {}, {}, {}], full_output=True)
assert_quad(res[:-1], 1.5267454070738635)
assert_(res[-1]['neval'] > 0 and res[-1]['neval'] < 4e5)
def test_variable_limits(self):
scale = .1
def func2(x0, x1, x2, x3, t0, t1):
val = (x0*x1*x3**2 + np.sin(x2) + 1 +
(1 if x0 + t1*x1 - t0 > 0 else 0))
return val
def lim0(x1, x2, x3, t0, t1):
return [scale * (x1**2 + x2 + np.cos(x3)*t0*t1 + 1) - 1,
scale * (x1**2 + x2 + np.cos(x3)*t0*t1 + 1) + 1]
def lim1(x2, x3, t0, t1):
return [scale * (t0*x2 + t1*x3) - 1,
scale * (t0*x2 + t1*x3) + 1]
def lim2(x3, t0, t1):
return [scale * (x3 + t0**2*t1**3) - 1,
scale * (x3 + t0**2*t1**3) + 1]
def lim3(t0, t1):
return [scale * (t0 + t1) - 1, scale * (t0 + t1) + 1]
def opts0(x1, x2, x3, t0, t1):
return {'points': [t0 - t1*x1]}
def opts1(x2, x3, t0, t1):
return {}
def opts2(x3, t0, t1):
return {}
def opts3(t0, t1):
return {}
res = nquad(func2, [lim0, lim1, lim2, lim3], args=(0, 0),
opts=[opts0, opts1, opts2, opts3])
assert_quad(res, 25.066666666666663)
def test_square_separate_ranges_and_opts(self):
def f(y, x):
return 1.0
assert_quad(nquad(f, [[-1, 1], [-1, 1]], opts=[{}, {}]), 4.0)
def test_square_aliased_ranges_and_opts(self):
def f(y, x):
return 1.0
r = [-1, 1]
opt = {}
assert_quad(nquad(f, [r, r], opts=[opt, opt]), 4.0)
def test_square_separate_fn_ranges_and_opts(self):
def f(y, x):
return 1.0
def fn_range0(*args):
return (-1, 1)
def fn_range1(*args):
return (-1, 1)
def fn_opt0(*args):
return {}
def fn_opt1(*args):
return {}
ranges = [fn_range0, fn_range1]
opts = [fn_opt0, fn_opt1]
assert_quad(nquad(f, ranges, opts=opts), 4.0)
def test_square_aliased_fn_ranges_and_opts(self):
def f(y, x):
return 1.0
def fn_range(*args):
return (-1, 1)
def fn_opt(*args):
return {}
ranges = [fn_range, fn_range]
opts = [fn_opt, fn_opt]
assert_quad(nquad(f, ranges, opts=opts), 4.0)
def test_matching_quad(self):
def func(x):
return x**2 + 1
res, reserr = quad(func, 0, 4)
res2, reserr2 = nquad(func, ranges=[[0, 4]])
assert_almost_equal(res, res2)
assert_almost_equal(reserr, reserr2)
def test_matching_dblquad(self):
def func2d(x0, x1):
return x0**2 + x1**3 - x0 * x1 + 1
res, reserr = dblquad(func2d, -2, 2, lambda x: -3, lambda x: 3)
res2, reserr2 = nquad(func2d, [[-3, 3], (-2, 2)])
assert_almost_equal(res, res2)
assert_almost_equal(reserr, reserr2)
def test_matching_tplquad(self):
def func3d(x0, x1, x2, c0, c1):
return x0**2 + c0 * x1**3 - x0 * x1 + 1 + c1 * np.sin(x2)
res = tplquad(func3d, -1, 2, lambda x: -2, lambda x: 2,
lambda x, y: -np.pi, lambda x, y: np.pi,
args=(2, 3))
res2 = nquad(func3d, [[-np.pi, np.pi], [-2, 2], (-1, 2)], args=(2, 3))
assert_almost_equal(res, res2)
def test_dict_as_opts(self):
try:
nquad(lambda x, y: x * y, [[0, 1], [0, 1]], opts={'epsrel': 0.0001})
except(TypeError):
assert False

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import numpy as np
from numpy import cos, sin, pi
from numpy.testing import (assert_equal, assert_almost_equal, assert_allclose,
assert_, suppress_warnings)
from scipy.integrate import (quadrature, romberg, romb, newton_cotes,
cumtrapz, quad, simps, fixed_quad,
AccuracyWarning)
class TestFixedQuad(object):
def test_scalar(self):
n = 4
func = lambda x: x**(2*n - 1)
expected = 1/(2*n)
got, _ = fixed_quad(func, 0, 1, n=n)
# quadrature exact for this input
assert_allclose(got, expected, rtol=1e-12)
def test_vector(self):
n = 4
p = np.arange(1, 2*n)
func = lambda x: x**p[:,None]
expected = 1/(p + 1)
got, _ = fixed_quad(func, 0, 1, n=n)
assert_allclose(got, expected, rtol=1e-12)
class TestQuadrature(object):
def quad(self, x, a, b, args):
raise NotImplementedError
def test_quadrature(self):
# Typical function with two extra arguments:
def myfunc(x, n, z): # Bessel function integrand
return cos(n*x-z*sin(x))/pi
val, err = quadrature(myfunc, 0, pi, (2, 1.8))
table_val = 0.30614353532540296487
assert_almost_equal(val, table_val, decimal=7)
def test_quadrature_rtol(self):
def myfunc(x, n, z): # Bessel function integrand
return 1e90 * cos(n*x-z*sin(x))/pi
val, err = quadrature(myfunc, 0, pi, (2, 1.8), rtol=1e-10)
table_val = 1e90 * 0.30614353532540296487
assert_allclose(val, table_val, rtol=1e-10)
def test_quadrature_miniter(self):
# Typical function with two extra arguments:
def myfunc(x, n, z): # Bessel function integrand
return cos(n*x-z*sin(x))/pi
table_val = 0.30614353532540296487
for miniter in [5, 52]:
val, err = quadrature(myfunc, 0, pi, (2, 1.8), miniter=miniter)
assert_almost_equal(val, table_val, decimal=7)
assert_(err < 1.0)
def test_quadrature_single_args(self):
def myfunc(x, n):
return 1e90 * cos(n*x-1.8*sin(x))/pi
val, err = quadrature(myfunc, 0, pi, args=2, rtol=1e-10)
table_val = 1e90 * 0.30614353532540296487
assert_allclose(val, table_val, rtol=1e-10)
def test_romberg(self):
# Typical function with two extra arguments:
def myfunc(x, n, z): # Bessel function integrand
return cos(n*x-z*sin(x))/pi
val = romberg(myfunc, 0, pi, args=(2, 1.8))
table_val = 0.30614353532540296487
assert_almost_equal(val, table_val, decimal=7)
def test_romberg_rtol(self):
# Typical function with two extra arguments:
def myfunc(x, n, z): # Bessel function integrand
return 1e19*cos(n*x-z*sin(x))/pi
val = romberg(myfunc, 0, pi, args=(2, 1.8), rtol=1e-10)
table_val = 1e19*0.30614353532540296487
assert_allclose(val, table_val, rtol=1e-10)
def test_romb(self):
assert_equal(romb(np.arange(17)), 128)
def test_romb_gh_3731(self):
# Check that romb makes maximal use of data points
x = np.arange(2**4+1)
y = np.cos(0.2*x)
val = romb(y)
val2, err = quad(lambda x: np.cos(0.2*x), x.min(), x.max())
assert_allclose(val, val2, rtol=1e-8, atol=0)
# should be equal to romb with 2**k+1 samples
with suppress_warnings() as sup:
sup.filter(AccuracyWarning, "divmax .4. exceeded")
val3 = romberg(lambda x: np.cos(0.2*x), x.min(), x.max(), divmax=4)
assert_allclose(val, val3, rtol=1e-12, atol=0)
def test_non_dtype(self):
# Check that we work fine with functions returning float
import math
valmath = romberg(math.sin, 0, 1)
expected_val = 0.45969769413185085
assert_almost_equal(valmath, expected_val, decimal=7)
def test_newton_cotes(self):
"""Test the first few degrees, for evenly spaced points."""
n = 1
wts, errcoff = newton_cotes(n, 1)
assert_equal(wts, n*np.array([0.5, 0.5]))
assert_almost_equal(errcoff, -n**3/12.0)
n = 2
wts, errcoff = newton_cotes(n, 1)
assert_almost_equal(wts, n*np.array([1.0, 4.0, 1.0])/6.0)
assert_almost_equal(errcoff, -n**5/2880.0)
n = 3
wts, errcoff = newton_cotes(n, 1)
assert_almost_equal(wts, n*np.array([1.0, 3.0, 3.0, 1.0])/8.0)
assert_almost_equal(errcoff, -n**5/6480.0)
n = 4
wts, errcoff = newton_cotes(n, 1)
assert_almost_equal(wts, n*np.array([7.0, 32.0, 12.0, 32.0, 7.0])/90.0)
assert_almost_equal(errcoff, -n**7/1935360.0)
def test_newton_cotes2(self):
"""Test newton_cotes with points that are not evenly spaced."""
x = np.array([0.0, 1.5, 2.0])
y = x**2
wts, errcoff = newton_cotes(x)
exact_integral = 8.0/3
numeric_integral = np.dot(wts, y)
assert_almost_equal(numeric_integral, exact_integral)
x = np.array([0.0, 1.4, 2.1, 3.0])
y = x**2
wts, errcoff = newton_cotes(x)
exact_integral = 9.0
numeric_integral = np.dot(wts, y)
assert_almost_equal(numeric_integral, exact_integral)
def test_simps(self):
y = np.arange(17)
assert_equal(simps(y), 128)
assert_equal(simps(y, dx=0.5), 64)
assert_equal(simps(y, x=np.linspace(0, 4, 17)), 32)
y = np.arange(4)
x = 2**y
assert_equal(simps(y, x=x, even='avg'), 13.875)
assert_equal(simps(y, x=x, even='first'), 13.75)
assert_equal(simps(y, x=x, even='last'), 14)
class TestCumtrapz(object):
def test_1d(self):
x = np.linspace(-2, 2, num=5)
y = x
y_int = cumtrapz(y, x, initial=0)
y_expected = [0., -1.5, -2., -1.5, 0.]
assert_allclose(y_int, y_expected)
y_int = cumtrapz(y, x, initial=None)
assert_allclose(y_int, y_expected[1:])
def test_y_nd_x_nd(self):
x = np.arange(3 * 2 * 4).reshape(3, 2, 4)
y = x
y_int = cumtrapz(y, x, initial=0)
y_expected = np.array([[[0., 0.5, 2., 4.5],
[0., 4.5, 10., 16.5]],
[[0., 8.5, 18., 28.5],
[0., 12.5, 26., 40.5]],
[[0., 16.5, 34., 52.5],
[0., 20.5, 42., 64.5]]])
assert_allclose(y_int, y_expected)
# Try with all axes
shapes = [(2, 2, 4), (3, 1, 4), (3, 2, 3)]
for axis, shape in zip([0, 1, 2], shapes):
y_int = cumtrapz(y, x, initial=3.45, axis=axis)
assert_equal(y_int.shape, (3, 2, 4))
y_int = cumtrapz(y, x, initial=None, axis=axis)
assert_equal(y_int.shape, shape)
def test_y_nd_x_1d(self):
y = np.arange(3 * 2 * 4).reshape(3, 2, 4)
x = np.arange(4)**2
# Try with all axes
ys_expected = (
np.array([[[4., 5., 6., 7.],
[8., 9., 10., 11.]],
[[40., 44., 48., 52.],
[56., 60., 64., 68.]]]),
np.array([[[2., 3., 4., 5.]],
[[10., 11., 12., 13.]],
[[18., 19., 20., 21.]]]),
np.array([[[0.5, 5., 17.5],
[4.5, 21., 53.5]],
[[8.5, 37., 89.5],
[12.5, 53., 125.5]],
[[16.5, 69., 161.5],
[20.5, 85., 197.5]]]))
for axis, y_expected in zip([0, 1, 2], ys_expected):
y_int = cumtrapz(y, x=x[:y.shape[axis]], axis=axis, initial=None)
assert_allclose(y_int, y_expected)
def test_x_none(self):
y = np.linspace(-2, 2, num=5)
y_int = cumtrapz(y)
y_expected = [-1.5, -2., -1.5, 0.]
assert_allclose(y_int, y_expected)
y_int = cumtrapz(y, initial=1.23)
y_expected = [1.23, -1.5, -2., -1.5, 0.]
assert_allclose(y_int, y_expected)
y_int = cumtrapz(y, dx=3)
y_expected = [-4.5, -6., -4.5, 0.]
assert_allclose(y_int, y_expected)
y_int = cumtrapz(y, dx=3, initial=1.23)
y_expected = [1.23, -4.5, -6., -4.5, 0.]
assert_allclose(y_int, y_expected)